My experience isn't broad enough, so I'm generally cautious when offering opinions like this, but the two branches of Boots I've used, one near home and one near my office (about 35 miles away) were both well trained, cotton gloves and the like. The Sainsbury's branch was poor, as was the Safeway branch (now Morrison's). The Jessops near my office was not bad at all, though I didn't care for their pay before collection policy. The Jessops near my home is good when it's the manageress who's on site, as she's sharp and knowledgeable, but not so good when it's one of the staff who has difficulty telling the difference between a roll of HP5 and a roll of Superia. I'm lucky in having a long-established family photo dealer nearby, staffed by people who know stuff about photography, and who can handle simple instructions that manage to confuse some of the non-specialist places, like when I want a dev only and uncut. So, true enough, I've found quickly those I can depend on, and stick with them.