They do indeed send them over here.
Spot on correct as their legal limit IS 4mm whereas ours is a very bad 1.6mm. It is also a legal requirement in some parts of Europe that you have to switch to Winters. They should apply that here too.
The place I got these part worns are graded for tread.
Grade 1 = 5mm or better
Grade 2 = 4 mm
5mm is plenty for a couple of winters. On the BM, my winter alloys/tyres go on in October and come off in March. This does two things for me. Firstly, comforted that, if driven sensibily, my car would get traction and give me the edge in stopping distance, and secondly, I'm not ruining a valuable set of 18s, be they salt attacked or bashed against kerbs.
Our GTi is on Sessantas and they didn't cope that well in the winter conditions, hence my initial question. Failing that, I could get all season tyres (Quadtracs) when the Sessantas need replacing, but that won't be at least another year.
Regards.