Rod G....Basically the further south you travel means you will need a larger dish to pick up the main UK Channels. In Spain you are not likely to pick up the UK BBC/ITV channels from Astra 28.2 if you are below the Benidorm area no matter how large your dish is.
We have an 80cm dish and free to air sat box and were able to get most BBC/ITV channels (except 5) when we stayed at Villanova Park, south of Barcellona. However when we moved further south to below Alicanti we could not receive them. However, we were able to pick up quite a few news and general entertainment channels, some of these are in English. You can also pick up a number of other satelites (Hotbird, Eurobird, Astra 19e, etc)
Also, go to the following site, it provides some good info on satelite coverage. http://www.satelliteforcaravans.co.uk/
Mal