Installing a fixed dish is relatively easy. For less limitation a motorised dish is much better. Installing is within the capabilites of anyone reasonably competent.
Lyngsat is the main bible of channels available on the various sats, there is also flysat and kingofsat.
Not sure what the B&Q one is but it is bound to be the cheapest and nastiest.(could be wrong)
Check out our site supporters (see my sig) One or two of them do motorised kits including receiver. The Technomates are good.
As for pay channels, you can buy a foreign subscription, which is what I have, there are also some packages you get get with appropriate software, not really kept up to date with what is currently available though.
Robbo