RRG generally get very favourable reviews here. Stockport, Bradford and Bolton are good. Whenever I've been to Manchester they have also been good.
The photographic evidence you mention is for Lexus UK to do their own checks as they pay the dealership for any work carried out. Therefore, a dealer could technically just vouch for any customer damage ie a smashed side mirror to fork out extra money from Lexus UK which is why they ask for it. Not the dealers fault on that one.