I have been with Zen for over 10 years, they are not perfect and I did have some issues a few years ago with what appeared to be congestion. I am on the
Tenbury Wells exchange, I don't think Zen have their own local loop connection (or whatever).
In general though they have been very good, both from a connectivity point of view and also customer service, they always pick up the phone, the people are always polite and seem to know what they are talking about.
I also have a PlusNet line, works OK but good luck trying to get any support from them.
Thing about support is, most of the time its completely irrelevant, but when you DO need it ..... its REALLY important.
So, I like Zen.
Chunks