Yeah i've left my card a few times and had to go back.
I even left the money once!
I like T/Checks....i know they are the dinosaur way of getting cash but i like to go to a bank and go through the whole process,i've met some really interesting people whilst queuing.
That being said ATMs are a lot easier but far too often i've been stood behind a fellow traveller and he/she has had their card swallowed....happend in April in Mexico,so its vital to have a back up card AND a c/card and some t'cs.
Read here http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2324216
Read about the downside of pre-paid cards. Read about Section 75.
You also need to understand that if you pre-pay something using a debit card it is the same as paying cash and you are not covered/insured in the same way as you are if you use a credit card. Book a flight for example and then the airline goes bust. If you used a debit card your money is gone and you are at the end of the long line of creditors with no real hope of getting your money back. Book and pay with a credit card and you simply fill in a form and your money is credited back to your credit card.
It is NOT wise to travel without both kinds of cards. You also do not say which bank debit cards you have. Not all are created equal. The site 365rtw provided is the best site for a traveller from the UK to use to see which cards to get.
Currently the best cc for a Brit to have is the Halifax Clarity card and the best debit card is the Norwich & Peterborough debit card. The issue is how much is it going to cost you in fees and exchange loading when you use your card. They differe from 0 in the case of the best cards to as much as 4.5% of your money in the case of the worst. How much is 4.5% of your total travel budget?
It is ALWAYS best to use a debit card to withdraw cash from an ATM and to use a credit card to pay/purchase things.