I've had an excellent experience with Xnet so far.
However, when I came to fill out the credit card payment form on the introductory brochure I was sent (section B) I noticed that after I'd filled in my details in ballpoint pen and figured out how to fold it, I could see my credit card details through the other side of the white side with the Freepost address. I don't push my pen particularly hard! This is my main gripe.
The following is a very minor gripe. Anyway, called up Xnet to give my details over the phone (pretty much instantly got a human as usual rather than a recording), and got another note to confirm my call, which was fine except that I couldn't find the freepost envelope. Oh well.
Would be grateful though if the brochure (and particularly the credit card bit) was made of stiffer material that isn't so easy to see through.