For the record, there is no legal requirement in the UK to carry ID.
Although, I'm sure having one could come in handy in several situations, especially if someone looks young and goes out drinking. I am not young, and even I have been asked for proof of age at a few bars and clubs, and I did not have anything to present to them. I got in anyway, every time, but, still... It might be good for me to get something.
I do not carry my passport because if it is lost, replacing it, with the visa, is so expensive, and such a pain!
I drove here for the seven months, before we moved into London, but after moving, I stopped. No need now - and if we do need the car, hubby likes to drive. So, I never got a UK DL.
After reading this thread, I have decided I will consider getting the provisional, as an ID, in the near future, as it seems like a good thing to have...