My newly acquired Avon/locost hybrid chassis has some nasty looking metalastic type bushes in the wishbones. They don't fit the inside of the 1" tubing very well, so I was hoping to get some poly bushes, preferably with a "top hat" shape so the bush protrudes either side of the tube. Can anyone recommend a supplier for these? The tubes on my wishbones are approximately 37mm long.

what is the id of the tube where the bushes will go?

Good point. Don't have my calipers handy, but it looks to be pretty much exactly 21mm or 8/10"

I would say that your tubes are probably too small in inner dia to accomodate pu bushes.
You need enough room for a bolt.. say 12mm and a crush tube say 17mm outer dia. or there abouts. This will leave a very small wall thickness on your pu bushes and they would either fail or not last very long.
Only my opinion though..

Currently using M10 bolts. The book only seems to use M8 so should be plenty strong enough?

If the tubes are too small, I'm happy to chop them off and weld larger ones on, as I have to remake the front wishbones anyway.

If you are going to replace the tubes then Luego do polybushes that are cheap, thats where i bought mine.

Thanks for all your help. Just ordered a set from Luego who have been extremely helpfull.