I have had issues with Overclockers.co.uk simply put I was banned twice for taking faulty items back to them.
Everytime I took something back that was faulty or broken to the point it didn't work anymore they just simply, came back to me saying there was no fault found and it worked fine.
1st time I was banned was because I took my brother in law to them, to return faulty items.
One of the items was a PSU that went pop and you could smell it had gone bang and the fan would not spin up on it or anything, unyet according to them it was fine and there was nothing wrong.
Another item was the ram which failed a Memtest+ test within the 1st 30 seconds, tested on another board after testing the ram that was in it already so I knew the slots were not faulty and neither was the ram in my system, but with his ram in my system it failed again.
The next was a graphics card that was giving artifacts in windows and games, and I showed a picture of the issue to the manager at that time, and he said the card was faulty and to return it to where I bought it from, so I got the box out of the car and handed it over, they went away and tested it saying nothing was wrong.
Over the space of 3 day's I must have driven to them and back home around 20 times, and each time regardless of what happened with the pc they always said everything was fine.
Eventually they said the items were faulty and then banned me and my brother in law for returning faulty items.
2nd time I was banned because I took a faulty board back to them, and they said there was nothing wrong but I only took it back because I had tested everything else in another pc, to make sure that the board was problem.
I asked to see it being tested and they instantly banned me on the spot, and when I asked why I was being banned again for returning a faulty item to them, they basically said I was being disruptive although I had remained calm and never raised my voice.
This time though I had to laugh because other customers in the store just looked shocked, especially the one customer who was there already when I got there and he could not believe it and asked for a refund of all the stuff he had just bought, because in his words he couldn't feel safe spending that much money only to risk being banned if something was faulty, and he saw I was not aggresive or anything.
I will say before those experiences OCUK were amazing and I recommended them to everyone because they always offered advice, and were always very cheap etc and I had never had a issue with them.
I now only use Scan because I can see stuff being tested, and I have returned quite a few things that have gone faulty and never once had a issue with them.
The simple thing is each person has there own experience with shop's, and if someone has a bad experience it will taint that shop forever, my bad experience was OCUK for others it's Scan or another.