Don't know if anyone can help us but we are doing a bit of filling on our house where a gas wall heater and plumbing pipes came out. We have been able to find some bricks which aren't a bad match but are open to suggestions but we are really struggling with the mortar, which is grey. We have put a couple of pictures in our album, which should be available to view. We live in a 1960's house in King's Lynn, Norfolk. Many thanks