What's the card-count for this - 78? Just wanted to check I had all the cards before I pack it away ready for playing at some point, but it doesn't seem to say on the box.

Yep, 78 is the card count

There are 4 encounter sets and each card will give a #x/total for the set

Set 1 The Blob That Ate Everything: 54 cards
Set 2 Mi-Go Incursion: 18 cards
Set 3 Single Group: 3 cards
Set 4 Epic Multiplayer: 3 cards

54+18+3+3=78