Poked down the plug hole and removed lots of grot - think it could have been a build up in the plastic pipe underneath from dog hairs etc. Anyway, as I poked with the end of a spoon it seemed to move and when I looked underneath there is a black piece of tube about 2 inches long that sits in the white u shaped pipe. This has come away from the underside of the plug hole and the seal that joins them seems to have disintegrated. I have stuffed something underneath to hold it up in place but obviously it is going to leak when I run the tap for long or empty the bowl as its not sealed. Can I get a new black bit which will have a seal on it or will I have to have someone come and stick it back.
Moved.... I thought you were going to tell us about some mysterious sink creature that had set up home in your waste pipe !
I would suspect anything you need would be stocked by your nearest local DIY shed. Go have a gander at what they offer. As for whether you can do it or you need to call in a plumber, well that depends on your confidence level.
But watch out - different plastic plumbing manufacturers have different ideas on how they measure a pipe's diameter! I've got all sorts of bends and straight bits kicking around, none of which fits the other, even though they're marked as being the same size.
Good point from Heathy. Some are called 38mm, and others 40mm.
I think Heathfield's main problem is that, in the trade, solvent weld is used. For DIY, push-fit pipe is a different diameter from the solvent weld.
Standard 40mm sink traps are interchangeable. They come with "screw-up" connections that have some tolerance in diameters that they'll accept.
I'm still puzzling over this black piece of tube. I can't think what that is. No matter, easier to replace the trap.