Where and how you live should be your own business, but if I were you I would ask the citizens' advice bureau or a solicitor whether there are any legal drawbacks - you don't want to be had up for defrauding the Inland revenue at some point in the future.
I'm assuming that neither of you have children, as you don't mention any, but whether you marry or not and whether you decide to live on board his houseboat or in your house, or turn and turn about, please avoid difficulties in the future by making wills (dreary task, I know) and check with your banks what happens with bank accounts, here even if you are married, you cannot access a spouse's bank account either during their lifetime or if you are left as a widow or widower. I know many people who discovered that sad fact too late! You need a power of attorney unless you have a joint account. This kind of thing is easier to discuss while you are both healthy than later on, if one of you is seriously ill.