I have a BSA B50 cylinder head which, unfortunately, is the victim of detonation and therefore requires repairing including welding and machining. It's a very good head and well worth the trouble. Can anyone advise on a quality engineering outfit that could tackle the job? I live quite near Manchester and, as I don't particularly trust Royal Mail it would be preferable but not essential if I could deliver and collect the head myself. Any suggestions would be gratefully accepted.