I bought a new 250 EXCF six days before xmas, it went wrong at 8.4h (had a service at 3h).
It was sudden, engine just cut out, turned out to be a sticky exhaust valve and a shim fell out.
Anyway, Premier Bikes did a belt and braces job and replaced everything associated with the valve, even the piston.
All work and parts were replaced for free by KTM as you would expect,
but also Premier Bikes gave me a hundred quid to spend in their shop as a gesture of good will.
So they are good guys and I would recommend them and use them again..