My wife found me some diabetic shoes and socks that are a looser fit and don't squeeze my feet too tightly. Like you, I have extra wide, flat feet to go with the neuropathy that I get to deal with everyday.
We found the socks in the pharmacy dept. at our local grocery store, and we ordered the shoes from Amazon. They're made by a company called Silent Care, and they're extra wide with a thick rubber sole that cushions your feet. They're not the most stylish shoes you can wear, but at this point, I don't care any more.
By the way, I'm envious, I've wanted to visit England for my whole life, but it'll never happen, we could never afford something like that.
Good luck, I hope this helps.