I've been with Zen for 8 years, but when I discovered there was 21cn at my exchange, and I wasn't able to get on it, I looked around for an alternative. I found AAISP a few months ago, as they promise to help fix rubbish BT lines if you have problems, so I bore them in mind for a friend / for the future, but did remember think they looked expensive compared to Zen (I was wrong btw).
Determined to get on the 21cn I looked again, and realised I would in fact get more download allowance for the same money than with Zen, and then called their support line to see if they could help at my exchange.
They could. One week later and I've jumped from the 6.5 mbps I've been stuck on for 8 years to a full 24mps - speedtest.net is reporting 20mps.
All the way along they have kept me informed, they sent me my choice of router, they are open about how they work and if you investigate a bit more, there is no stupid traffic shaping or any of that going on, just perfect internet access with great support. They even phoned to check all was well once the link went live.
I couldn't be more pleased or recommend them more highly.
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