Gav - I'm arranging breakdown cover through the ADAC, but I haven't tried with insurance. I did ask about insurance but the guy I was speaking to was unsure wether it was possible.
Problems I foresee are, having a UK car insured abroad (but still in the EU) may mean that it isn't listed on the MID (motor insurance database), that all the ANPR cameras are linked to, so you may end up being pulled over regularly and being acussed of having no insurance. If you can't prove that it is legally insured then the nice police man can seize the vehicle till you can prove to them/satisfy them that it is legally insured.
As Andrew says, another problem maybe the issues encountered if you were unfortunate enough to have to claim. The insurance company would need to have reps in the UK to be able to assess a car and arrange a repair, let alone possible problems of a language difference. Etc.
I do wonder if it's even possible to insure a UK car in another EU country for a full year? I would have thought that if you did need to insure your UK car in another EU country, that they would only do it on a temporary basis, 1 month - 3 months - 6 months sort of arrangement? I reckon to get a years cover you'd atleast need an address in the relevant country before they'd even entertain the idea, but I'm happy to be proved wrong.
Insuring a modified vehicle is an awkward task, and at the moment, a rather expensive one.