Well after much timewasting searching web sites, reviews, etc. and listening to advice here and elsewhere I have bought my replacement laptop (to replace my Thinkpad T430).
I decided to stay with Thinkpad Txxx as reviews indicate they are some of the best machines around *and* they are good for Linux.
Rather more in hope than expectation I bid for a T470 on eBay and got it for £650. The T470 is the current T series model and this one has a latest (7th) generation Core i7 processor, 8Gb memory and a 256GB SSD. It is ex-demo and thus virtually unmarked and comes with a full 3 year on-site warranty! New price is around £1500.
Wow! :-)
I have installed xubuntu 17.04 on it and it's lovely! :-)