It would probably be a good idea to get the digibox and card in the UK before you go to Spain as you will pay a lot more for one there. The pace 2700 and new grundig range have good tuners for weak signals.
Your dish won’t be big enough for all channels, but you should be able to pick one up locally once you know the size you will need. Probably in the region of 1.2m, but try and find out locally before buying one.