As suspected Halfords doesn't open till 10 am but 24 hour Shell garage had the right stuff and it's only 2 miles from my house (forgot about that one) and sure enough there's a picture of a motor bike on the bottle (and I rang Ali to check it was the right stuff). I think maybe even a rudimentary knowledge of these things would be a big plus for me so I'm definitely going to try to be less hopeless - Dr AK I'll be wanting more detail about where to put the sawdust.
Thanks for the help guys. Should be all sorted and it's going to be warm and sunny tomorrow. Hoorah!