I have now got most of the jobs done I wanted to so will be attemp to remove the pesky bolt tomorrow . I will update my progress . Thank you to everyone for your time and advice .
Ok well finally got it out today with the help of a neighbour and his tig welder . He welded a nut onto the bolt and we both reckon it was the heat that did it as none of the previous options worked . Anyway I can get everything back together again as I have a replacement bolt ready to go.
Thanks again for everyones input
Tell me about it .......my neighbour has worked on loads of vehicles and race bikes and he was just as surprised . I`m glad I had someone else with me as a sanity check . Tried the new bolt today just gently winding it in and out a bit further each time and all seems to be ok .