I don't recognise the description - how many engines ?
As far as I'm aware, apart from the Duxford-based Blenheim, there are no single-finned 'bombers' airworthy in the UK.
However, there are at least three airworthy Dakotas (C-47 / DC3), with the RAF's BBMF having an example in Olive Green with Neutral Gray undersides. Another is camouflaged, but I don't know its current colour scheme.
There is also a camouflaged (as above, BBMF example) at Elvington, near you, which is capable of engine runs, and was aiming to become airworthy again, although I don't think it is yet.
Below are a couple of pics of the BBMF Dakota, and a formation of US based examples which were in the UK in 2014.
Perhaps this is what you saw ?
I forgot to add - there is, of course, 'Sally B', the Duxford-based B-17G, but that doesn't have yellow stripes on the fin. Pic below.