I have recently changed from Claranet to Naims.
I have had no trouble with them, in fact I asked them a question by Email last night and had a reply this morning. I also asked them an emailed question about two Sundays ago and virtually had a reply straight away. I had been with Claranet for a couple of years and realised that I was paying through the nose for a good contention ratio and now I have virtually the same contention ratio for half of the price with Naims! So far so good, but I don't think that I shall stay with them for Broadband as I think F2S seems better!