My 2 worst as they were both as bad were plumbcenter and pts in Gloucester. Parts not turning up loads of damaged bit delivered and poor staff who basically couldn't care less.
Generally speaking though I find the bigger the branch the more the problems. My old local plumbcenter and pts were brilliant (had a problem with plumb once and that was the manager) they were only small branches and didn't just go for the big companies as there wasn't many.
You will always have problems it is just how they deal with them. I had a problem with a Williams order (3 problems on 1 order actually) and had to go to plumbcenter to get me out of trouble and have started using them a lot more now as it is easier for a company to solve a problem when they are 20mins away rather than 4-5 hours.
Generally speaking though I find the bigger the branch the more the problems. My old local plumbcenter and pts were brilliant (had a problem with plumb once and that was the manager) they were only small branches and didn't just go for the big companies as there wasn't many.
You will always have problems it is just how they deal with them. I had a problem with a Williams order (3 problems on 1 order actually) and had to go to plumbcenter to get me out of trouble and have started using them a lot more now as it is easier for a company to solve a problem when they are 20mins away rather than 4-5 hours.