Okay guys, thanks for the advice, I’ll tackle this today. It was the last job I needed to do yesterday and had me stumped. I have a Dremel and drill bits. The bolts are tiny aluminium bolts with the screw part around 1mm in diameter so I’ll try drilling the head off first. Because of the location, I’ll need to be extra careful not to damage the frame, hoses, levers, etc.
It’ll be embarrassing to have to take the bike to my LBS to remove a pair of grips! I really find the stock grips uncomfortable and have a pair of Ergon GA2 grips that I want to use.