Teddy, did you have an luck? I also have a Mercian frame and have ahd the seatpost in the same place for ages as a result of it being fine and also becasue I don't have an allen key for it. However yesterday, my bike took a slight knock and the seat post moved so I would like to tighten it. If I can get a key, I'll also take the post out to clean etc.

Could you let me know if you found one in a shop or if you managed to borrow one from somewhere.

Thanks

Joe

p.s my email is jtsilvester[at]hotmail.com