The Defiant-class Light Cruiser in Battlefleet Koronus is listed as comeing pre-equipped with two Jovian-class Launch Bays.Given the fact the vessel is a Light Cruiser, should these actually be Escort Bays instead? The Components list implies this should be the case, but I wasn't sure if it is supposed to be a special feature of this class of ship - it can carry a much larger landing bay than a ship of its size normally can.

If you compare the crew numbers for the Defiant (6,100 pilots and support crew) and the Dictator (15,000 pilots and support crew) the larger Cruiser has more than twice the number of pilots and supprot crew. This implies double the number of small craft/squadrons which would be in line with the smaller vessel using an Escort Bay.

On an associated note, is there an errate for Battlefleet Koronus?

There's no official errata for Battlefleet Koronus, but I've been collating the various official responses to questions posted. The Defiant hasn't come up before to my knowledge, which is a little surprising.

Anyhoo, BFK Errata:

Chapter 1: The Weapons of War
Table 1-5: Lance and Macrobattery Craftsmanship Modifiers (Page 18): Ship Point and Morale modifiers are not among the modifiers that you can choose to be affected by component Quality. You get those automatically, choose from the other categories.
Table 1-8: Essential Components (page 33): The Mezoa-pattern Theta 7 was not listed and has the following profile:
"Hull Type: Transport
Power: 44 Generated
Space: 18
SP: +1"
Table 1–9: Starship Weapons (Page 35): The Strength value for the Voidsunder Lance Battery should be “3".
Table 1–10: Supplemental Components (Page 41): The SP cost for Bombardment Cannons should be "3".
Table 1-11: Archeotech Components (Page 42): The entries for the Plasma Accelerated Torpedo Tubes and the Nova Cannon should be ignored; use the profile in Table 1-12 instead.
Table 1-11: Archeotech Components (Page 42): The Warp Antenna's Space is listed as 1; it should be 0.
Assault Boat Operations (Page 16): The sentence that reads "Make a Challenging (+0) Command+Craft Rating Test (this will either be from a character aboard the carrier, or from a character leading the assault boats personally), gaining a +5 bonus for every squadron of friendly bombers after the first." should be changed to "Make a Challenging (+0) Command+Craft Rating Test (this will either be from a character aboard the carrier, or from a character leading the assault boats personally), gaining a +5 bonus for every squadron of friendly assault boats after the first."
Exorcist Grand Cruiser (Page 21): The Jovian-pattern Launch Bay Components this ship is equipped with should be listed as Jovian-pattern Landing Bays.
Mars Battlecruiser (Page 22): The Jovian-pattern Launch Bay Components this ship is equipped with should be listed as Jovian-pattern Landing Bays.
Hold Landing Bay (Page 36): As the Hold Landing Bay replaces the Main Cargo Hold, the Achievement Point bonus it grants is lost. In addition, the Power cost of the Main Cargo Hold is replaced with the Landing Bay's cost of 1.
Manufactorum (Page 39): The sentence that reads "If paying for repairs, each Manufactorum adds a +10 bonus to the Acquisition Test to restore Hull Integrity." should be changed to "If paying for repairs, a Manufactorum adds a +10 bonus to the Acquisition Test to restore Hull Integrity." Only one Manufactorum is possible on a ship.
Plasma Scoop (Page 40): This Component should add +25 Achievement Points, not +5.

Chapter 4: Rules of War
Crew Population and Morale (Page 115): The sentence that reads "NPC starships are able to sustain an amount of Crew Population or Morale damage equal to their ship’s Hull Integrity plus Crew Rating." should be changed to "NPC starships are able to sustain an amount of Crew Population or Morale damage equal to their ship’s Hull Integrity plus Crew Rating Bonus (The first digit of the Crew Rating)."

Frequently Asked Questions
Q. Is it possible to combine Armoured Prow Component + Power Ram? Or Armour Prow + Reinforced Prow? Or Reinforced Prow + Power Ram? Or Armoured Prow + Reinforced Prow + Power Ram?
A. You can combine a Power Ram with an Armoured Prow, or with a Reinforced Prow. You cannot combine an Armoured Prow with a Reinforced Prow, or all three together.

Q. Do shipboard combonents that add to Hit + Run action in shipboard combat (barracks + murder servitors, for example) work on Boarding Torpedos?
A. This is a matter of common sense. For example, Murder servitors would probably work with Boarding Torpedoes, because you could fill your Boarding Torpedoes with Murder Servitors. However, a Barracks has to be transporting troops to give the benefits in the first place, and it would depend on the troops in question. Elite forces such as Stormtroopers, void-trained Imperial Guard, or forces along that ilk would give the bonus. But a Regiment of conscripts who barely know how to fire lasguns would probably be more of a liability than a benefit.

Q. Do shipboard combonents that add to Hit + Run action in shipboard combat (barracks + murder servitors, for example) work on Assaukt Craft?
A. See previous answer, with the additional caveat that Assault Craft are easier to survive in, and don't require quite the rigourous skill-set that using a boarding torpedo would. So in that case, your conscripts might actually be useful.

Q. Are the increased Ship Point Costs (and therefore corresponding increased difficulty at acquisition costs) for Good + Best Quality shipboard components in Battlefleet Koronus in addition to, or instead of the usual -10 and -30 to acquisition tests for good + best quality.
A. The Ship Points modifying Acquisition Tests specifically apply to procuring either ship hulls or full starships. So if you're buying a hull, or buying a built starship, you'd modify the test by the Total Ship Point Cost. If you were buying the Component individually to install on an existing ship, you'd use the Acquisition Test modifiers for Good and Best Craftsmanship instead.

Q. If a Crew Reclamation Facility (reduce damage to crew population by 3 to minimum of 1) and a Bilge Rat Quarters (reduce damage to crew population caused by depressurisation by 2 to a minimum of 0) are combined, in what order do they function? IE: if a ship takes 3, 4 or 5 damage to crew population due to depressurisation, is it reduced to a munimum of 1, or a minimum of 0?
A. In the specific case of depressurisation, you'd reduce the damage by 5 to a minimum of 0. In other cases, of course, they wouldn't stack.

Digging out my copy of Battlefleet Gothic: Armada for reference- I'd say it looks likely to be the Jovian Escort Bay (the Exorcist and Mars both have a listed squadron strength of 2 per bay, the Defiant has 1). Speculative, but possible. For reference, the Dictator has a squadron strength of 2 in BfG, too.