Some information which may help.
Firstly regarding who fits the brake pads (I do my own). Although absolutely critical, this is probably one of the easiest and straightforward jobs on any car, so although I am not at all keen on having mechanical work done at a fast fit tyre garage, this is one thing that they should be able to do. Having said that, they will probably fit the cheapest nastiest pads, so be sure that you specify and insist on which make are fitted.
As for which make of pads to fit, I would recommend Delphi (formerly AP Lockheed and F1 supplier), Ferrodo, Lucas/Girling/TRW (if you can find them!). I replaced the Japanese pads with Delphi which made a big improvement, not in stopping as previous did that well but snatched making a smooth stop very difficult. Basically the brakes were full on or full off. With the Delphi the braking is progressive, far more driveable but still does the emergency stop to the max when called for (due to other drivers doing something silly obviously!). Pagid make a real sticky mess of your wheels from what I have seen, but I haven't used them for some time.
I found a problem getting the old pads out. The callipers on my car had some copper spring clips between the edge of the pads and the sliders. These were so tight, jammed in fact causing one pad to wear out. Removing the pads involved hitting very hard with a hammer, no other way. I decided after serious examination and much consideration to fit the new ones leaving these clips out. After all other cars do not have these. Not a decision I came to lightly but I could see no need for them and they caused all of the problems. The road test seemed fine so left it like that. The MOT was soon due so got that done as the ultimate and severe test their would find any issues. None at all, brake test spot on. Would be interested to hear if anyone else had any issues with these clips, or if they have been deleted from later production. I suspect that the production pads may have been smaller in that area with the clips and later pads were bigger without clips.