A happy customer (touch wood...)
I decided to move from Sky to Plusnet as they were offering free broadband for a year with £50 cashback and Quidco were offering a further £110 cashback. Plusnet paid out by cheque fairly quickly, but the Quidco cashback claim was rejected. Maybe it would have gone through if I hadn't claimed the £50. Anyway, about 4 months later Quidco emailed to say the cashback claim was rejected due to an error on their part and they've now kindly paid out as a goodwill gesture. Thanks, Quidco!
As for Plusnet, the switch-over was delayed from my requested start date for some reason, but when it happened it went smoothly. The ADSL connection is usually slightly faster than my LLU connection with Sky. For the first couple of months it was a bit unreliable and I had to do frequent router restarts, but it has settled down now and I haven't had any problems at all for the last few weeks. So, it took some time to get things sorted out, but I'm now a happy customer.