1) I personally don't think I'm stupid but the range of options
for getting into Manhattan for an afternoon / evening is huge! Any suggestions?
Also for getting back! We've an airport hotel booked
for the night.
Take an Amtrak or NJ Transit train to Penn Station in Mid-town New York...by far the quickest way! Shouldn't be too expensive.
2) Seriously, what are check in times like at the moment? Is the UK 2-3
hrs in advance going to be enough?
Depends on the airline/time/plane size etc etc. It's only a 757 with less than 200 seats so I'd say 2 hours is enough. Go at whenever Continental says you should go!
3) Why on earth did I decide to do a course that sees me spending
1-2hrs a time underwater and in a cave?
I'm afraid I can't answer that!
4) Go on, what's the must eat there place for Manhattan?
Depends on your tastes/budget. There's plenty to eat around Times Square - my personal favourite is the Hard Rock Cafe - huge burger, drink and 'fries' for around $10.
5) What is the Continental service MAN - EWR 757 service like?
I flew this a few months ago and it was quite a good flight. Outbound had AVOD at each seat but the inbound had overhead screens. I would use Continental again with no hesitation!