I dunno I would say that most of the people I know from all age groups, all voted in a variety of ways, I know several people younger than me some in their early 20s who voted leave, I know of one in particular, she would be in her mid 20s, who when I asked her how she intended to vote, replied "in what?" I said "the referendum" she replied "the refer what?" I said "how are you going to vote, leave or remain?" "leave or remain what?" "the EU" "what's a EU?", I gave up at that point.

an elderly couple I know who are staunch Tory supporters voted to leave saying that it didn't feel right to not support a Tory PM but they were determined that leave was the answer, I couldn't help wondering why as they are both in their 80s.

I also know a few less 'political' friends who voted leave because Cameron was in favour of remain, and one or two who 'don't like immigrants'

The idea of an "associate citizenship" is legally absurd. Citizenship is a fundamental concept with rights and responsibilities to a country. You can't be a part-citizen.

Anyway I wonder how Brits in Spain will fare if they are required to pay their own healthcare? Or if they are forced to sit a test of language and knowledge similar to the 'Life in the U.K' test here?

The notion of EU citizenship is legally absurd. The EU isn't a country.