Hi again. Yes, literally knock on the door! A farm house is reasonably obvious and may even be called a farm. If there are lots of dogs I’d avoid but often you find an obvious spot. Eton wick is a possibility on the flood plains. There’s a farm there you could try when the cattle aren’t in the fields. Just stay clear of the road and river. You might even be able to fly around the Millennium River but check the by laws on the RWMB website.
Oakley is also a good idea. Maybe check with the hotel to find it if they know who owns the land - they may do themselves.
The Crown Estates are usually pretty tolerant too, so you could ask at the Royal Windsor Farm Shop for contacts?
I know it’s not straight forward, and around Windsor just be mindful of Heathrow’s CTR and watch out for any Notams in the area, but honestly, you’ll find a spot and love it.
You could also get a Mavic Mini. Being less than 250g you don’t need to worry as much as its unlikely to cause much damage. I often take this out on walks and as long as you stay a good distance from people (150m without a PfCO) no-one’s going to mind much of you fly this over a field. They’ll barely see it or hear it.
And I can also recommend a Husban X4 (without camera) which you can fly inside your house. They’re tricky buggers as fully manual but it will improve your flying skills no end and provides a cheap thrill.
Hope this helps and if I hear of anyone with land near you, I’ll put you in touch.