Lots more choice above 125cc
Well Pete3, you are moving up a bit in CCs with the small XTs, but I have to agree with The Cameraman - the Serow XT225 is a great small bike with simple mechanics and a low state of tune which should be good for a long engine life, as per Cameramans' experience.
Of course it is not the fastest machine on the road and, personally, I would not want to run mine at up to 60 MPH for too long (major highway work is not it's strength).
It is easy on self maintenance and has very few weak points; it has a very small oil content in the sump so that needs to be monitored closely.
It was never imported into the UK officially (maybe imported officially elsewhere in Europe?) but there are a few around in the UK having been brought here from Japan.
The latest version is now a 250cc capacity and these are also being imported here - they can be found in ebay for example.