Well, I can understand OP's desire to have everything arranged discreetly, not so much for his benefit but to spare his next of kin any undue upset or embarassment. It would be quite the double-whammy for his (future) widow to first lose him, then a couple of weeks later discover his £5000-a year habit at Big Brenda's Massage Parlour.
Just to addend my previous post also, I'm not sure why simply keeping a stash of cash would draw suspicion - compared to all the skullduggery of opening new accounts and having bank cards sent to PO Box addresses and so on. (What happens if you have these secret cards, and punting phone, on you at time of death!?) A couple of hundred a month withdrawn from an ATM could be easily explained away as cash for haircuts, tips when at restaurants because you don't believe electronic tips get fairly shared to the staff, beer money because you like to have a tangible budget so you don't get carried away... you get the idea.