What you are looking for is probably Sticky Toffee Pudding. What I've learned after 2 years in the UK is that 'pudding' refers to almost any dessert.. and it's not anything like what gets made from Jello Pudding mixes. The more traditional places like Rules and Simpson's will probably serve this as a dessert and be very good. Here's an interesting website I found with some thoughts on Sticky Toffee Pudding... even used as an ice cream.
A recent article in the Guardian said that younger people(40 and less) are not interested in such old-fashioned 'puddings', but they are available in many places. On a recent trip, I had Spotted Dick at Sweetings, a fish restaurant in the City, while the guy next to me had treacle pudding. Mine was an amusing dessert, though not something I would repeat: it seemed to be made of whole-wheat bread bits mixed with white raisins and covered with custard. The treacle pudding looked the same but had a syrup over it. Anyway, I had to try it. Good luck with your search.
well, i love the guardian but i think they are way off the mark with this one. every time i make sticky toffee pudding it receives major kudos from everyone - a twenty something guy recently pronounced it pudding of the year! :)
first and best i ever had, beside my own, which is wickedly decadent, was at the mason's arms in cartmel fell in the lake district. yum.