Excellent.

My iPhone 4 recently had it's screen replaced by someone else, and they messed up the signal, so I wasn't getting any signal or 3G. Sent my phone to these guys for a diagnostic, 3 days later they emailed me saying they had found the problem and have fixed it! Then they sent the phone back the next day, so I sent it on Monday, got it back on Friday. Excellent service, customer service was really helpful and I used the live chat a few times.

To some people 5 days for a fix is too long, but they stated it'd take 3-5 days beforehand and I was fine with that. In total I paid £30, which is a bargain as my phone now has full signal and 3G. If you need to get your phone fixed, use these guys.