Not sure on dish size for that part of Spain, I know there's apparently a null around Barcelona where it's very difficult to get any signal on the UK channels.
Otherwise you have the option of the Freeview digital terrestrial back-up feeds on Intelsat 905 (27.5W). This is a different satellite than those used by Freesat, but the signal is stronger in south western Europe. 80-90cm should work fine in Catalonia.
For this feed you will need a compatible receiver (the channels are encrypted to stop rights holders kicking up a fuss - we can't go into details on this but there is a long thread on this forum that talks about the system -
uk bbc channels normally on 28.2 on intelsat 907 27.5w ? ). There are a few receivers mentioned that work. This feed carries the main five terrestrial UK channels (BBC One, BBC Two, ITV, C4, C5) in HD, as well as the BBC digital channels (News, Parliament, BBC4, CBeebies, CBBC) and BBC radio.
There's no guarantee for how long this service will remain available, but it's been on there for around 10 years now. It might be your only viable option if the Freesat signal is too weak and you can't use the internet.
Your other option would depend on the speed of your internet connection in Spain. If your speed is fairly decent, and if you have family/friends in the UK who also have decent internet and some tech knowledge, you could get them to set up a small TV server for you. A tiny cheap PC like a Raspberry Pi works fine, with a TV tuner connected to a TV aerial. You'd then stream the Freeview channels over the internet from that. Essentially your own private VPN-style IPTV.