[Closed] RooferTrackWorld

Advice needed....
Had a replacement flat roof fitted by local building firm. All was well until I checked the final work after they left and found that the new roof has been patched twice. Phoned the owner of the company and he admitted the roof shouldn't have been patched and the patches are because the builders knocked a slate of the roof. Obviously he's not keen on replacing the entire roof and said the patching doesn't invalidate the warranty although I appreciate the roof won't leak, I'm not happy that the builders left and didn't mention the patching on a brand new roof. They've not been paid for the work. If he refuses to replace the roof what are my options legally?