both helicoils and timeserts will require the removal of the bracket to facilitate insertion and they can both be very expensive especially if you can't get anyone to do it and have to buy a kit.if the bolt doesn't get that close to bottoming out in the thread then i would get a longer bolt but use the old one to chase the thread,grind a flat on one side of the old bolt and wind it in with plenty of lubrication,it will basically do the same job as a tap then fit the longer bolt,make sure you get all the galled ali off the old bolt first though.
that city and guilds wasn't wasted on me after all then!,and i got to learn some big words as well!