How about calling this bloke?http://gme.jp/arch/images/angle.jpg

I think Angle Grinder Man specialises in wheel clamps not pointing!

Thanks for the responses.

I'm not so keen on using an angle grinder - not least because they
terrify me - but also because I'm planning to do a bit at a time.

The Screwfix plugging chisel is what I already have and it's too wide
(although Screwfix don't actually say how wide it is!)

The other Screwfix item looks interesting but I'd need an SDS drill.

I think I may end up grinding down the one I have