Thanks all, charger came yesterday and am pleased to say it worked. Was a little worried as it didn't look very er...quality? Stuck it on 12V and left it on for 6 hours and the battery seems to be back to normal.
Did make one silly mistake though as I was worried about frost on the bike, I chucked the rain cover it when it was still hit and now have mlted black plastic all over the header pipes
This has happened to me in the past, re heat it then wipe it off with a big wodge of rag (mind you don't burn you self) better than scraping it off which can leave scratch marks. Polish up again when the headers are cold.
There would appear to be a surfeit of prolixity and sesquipedalian content today please do not use a big word when a singularly un-loquacious and diminutive linguistic expression will satisfactorily accomplish the contemporary necessity
Use a natural fibre rag! Nylon or polyester would probably make things worse. I would use a stanley knife on a cold pipe for the worst of it, then polish with solvol autosol.