They really don't know what they are doing.
I asked them to skim a head (and remove/refit cams to do so) and pressure test it as I'd warped the head. So they removed cams & pressure tested it, then measured the warpage. They then phoned me to tell me the warpage was too large to be able to guarantee the head.
I asked why they didn't measure first (as that would be the easiest of the tasks asked of them) so as to avoid the unnescessary work already done if the head was too warped and they said that was just the way they did it.
I checked and decided the amount needed to be skimmed would be ok and asked them to skim the head.
When I got it back I found they had put the cams on wrong, exhaust on the inlet side and intake on the exhaust side.
I would assume since they had demonstrated this degree of incompetence they would have made no effort to keep all the valves and hydraulic adjusters in order either and for all I know didn't bother with the special bmw tool (or equivalent) needed to compress the valves in order to remove and refit the cams correctly and who knows what else they've done wrong.
So, that's Coventry Boring and Metaling in Coventry, earlsdon area. Prize cowboys.
If you are looking for somewhere in Cov you could try Chesmans Motorsports, they were more expensive but I've heard good things about them.