I have been looking for this for 8 or so years now. The large Paulownia I have is at long last doing the biz. I looked up at the blackbird in its newly bared branches and there they were, flower buds, lots of them.
This is not tomentosa but another species, kawakamii, one that is more seen in places with a warmer climate. It is a street tree in California and also can be a pest there as well, but not really in the UK. What is more important is this is one I grew from seed. This one is apparently know as the Sapphire dragon tree and not surprisingly with a name like that it is Chinese. Well it certainly looks happy enough here, just where it would normally get sun, it gets rain, lots of it!