Thank you all so much for this very valuable advice and context for what I would like to do. I really appreciate it all, and apologise for only coming back to it now. We moved out of our house of 9 years in England this week for an extended stay in Crete, and we're then moving to London in September, so it has all been a bit fraught in the Sarah household!
We're here now in the pouring rain in Roustika, to discover a leaking chimney in our big sitting room has resulted in flooding and rotting carpets, but our internet is alive and well, which is of course the most important thing... My husband has gone off to Vamos to collect all our new heaters etc. from England from Jon & Sheila, and soon things will start cheering up! At least this year we didn't get damp/mould... Unfortunately, the layout of our house, so charming in summer, means that to get from one room to another you have to go through the courtyard in the pouring rain! Any bets on how quickly our new au pair, arriving next week, gets back on a plane to Germany?
Anyway, as soon as the rain lets up, we will be exploring the local fields that have derelict cultivation (there are many) and identifying those that appear small enough, and we will keep the water issue in mind. Grapes may thrive in the most appalling conditions, but we need some water to get them started off! It's something we would like to experiment with now, and then invest more in down the line. A lease might be an excellent solution - thank you for suggesting it above.
We also found that although there was a ballpark figure for a house in this area, it was heavily influenced by the sentiment of the owner - we were asked for €100k for a tiny plot with a ruined shed (which no doubt once housed a family with 10 children!), but got our house very reasonably in the end.
I'll let you know how we do in the coming weeks - and no doubt ask for further advice - if we aren't washed away in this rain!