My experience with ICUK for anyone who is considering them:
I switched to ICUK recently and then suffered from an intermittent connection problem caused by some faulty wiring.

Throughout this, ICUK were first class, going through all the options and possibilities via email and each email i sent received a prompt (sometimes within minutes) response, from the same chap who knew all about our problems. They arranged for a BT engineer to call round and eventually everything was sorted.
I changed isps originally because of bad experiences with customer service, and have found icuk to be a breath of fresh air. Broadband as it should be!