Slightly smaller than a robin, uniform grey-brown, persistent single note call, very active, flits from tree to tree, sometimes seems to run up the trunks, likes oak trees.
Thanks folks, I'll have to look again, especially for the white underside. It's a hard bird to spot. I may have made too much of the running up tree trunks, but it definitely flits about a lot with this persistent single note call. I know where I can find it regularly, I could have got a photo this morning.
It's song has been likened to a squeaky tap being slowly rotated. This little mouse like bird always goes up, never down, unlike the Nuthatch that goes both ways.
Catso, I've just found out the last bit of info as I wasn't sure either if the Treecreeper was a one-wayer or a two-wayer ;-)
It's a nut hatch, I've seen quite a few over the last few years, the first one I saw I had to rub my eyes in dis-belief as I thought only wood peckers could go up trees. I asked around and found out what it was, it's the persistant single note that gives it away.
Thanks everyone, I am utterly intrigued by all this now, and looking forward to the bike ride home. Infuriatingly I can't get sound on my work pc so I can't listen until this evening.
I hope it stays still for long enough next time I see it !