Yesterday I saw a football-sized ball of mistletoe in a street tree in Leyton High Road!
I think it was in a rowan tree by the few berries left. Looking in a tree book today at a tiny picture of rowan bark makes me a bit more confident of that, but I have put it in my diary to go and check in a month or so's time.
I might have a go at tying up a sprig of mistletoe on a low branch of the ash tree overhanging my garden in the hope that the birds will spread mistletoe there. Perhaps the Organic Lea/Leytonstone Transition Town stall might have local mistletoe at Christmas.