Thanks all, really good advice, will be packing a small cooler bag and do some snack shopping before we board, good to know there might be a few options on board too. It's crazy the bars don't stock crisps, or it is to me, guess it's just cultural (a pint of lager (or any drink in a pub/bar) and a packet of crisps (chips) is common place everywhere in Britain, pretty much as quintessentially British as tea and toast, roast beef and the Queen!)
Thanks again, really helpful.