1) Foreign usage fees to be free
2) Some kind of interest free period (the longer the better)
I’ve not seen any travel cards with more than the standard “pay by your balance due” free period.
3) A high credit limit (£5000 upwards)
This largely depends on a variety of factors, including but not limited to, your income, your credit history.
If you are going travelling for 3 months, it would imply either students, or a non-full time job with cash to spare. If that’s the case a £5k limit is out of question. If you’ve been lucky with a job given you unpaid leave, the only card from the travel cards, in my experience, who will give you £5k would be Barclaycard.
Again, it depends on your credit history and your income.
Why do you need a credit card with 0% interest? Why do you need a £5k limit?
Could you not save the money and then go? If you are students, could you not get an internship, part time job?
USA (I assume that’s what you mean by “America”) is very expensive in terms of hotels, food, and drinks out compared to the prices here in the UK so expenses can wrack up very quickly!