Surely it has to be Spain. Don't be put off by the stay allowance as you are allowed up to 90 days in a 180 day period; in other words 180 days a year. I would avoid caravans especially in the UK; I looked into it. All googling led me to the conclusion the whole thing is a rip off - expensive site fees; rules that prohibit sales unless done through the site operator; renting out through the site operator only with hefty charges and you have to change your caravan every 10 years or so. And of course the weather in the UK is so unpredictable.

I would look into renting an apartment in Spain without the hassle of ownership.