Post '96 is the way to go for a number of reasons:
1. Post '96 DR650 is still in production, parts world wide.
2. Post '96 has loads of owner and aftermarket support, Pre '96 has very little,
parts can be hard to find.
3. Most important ... post 96 is the better bike ... by far. Significant upgrades from earlier model.
Keep reading, research. The DR is not perfect, but close enough.
Buying in USA is, IMO, best alternative. You may find imported DR's in UK but fairly rare and a bit expensive. Old ones tend to be junk. Not worth the trouble.
California and Arizona have many DR's for sale every week ... prices can range from $2500 USD for older too $4500 USD for newish low mile example. A dealer can help get the bike registered in your name and get insurance.
You've picked the best (IMO) ADV bike made in the last 20 years. Learn it's ins and outs, do the proper upgrades and you'll travel an easy 65,000 miles trouble free in comfort.