There has been quite a few people on here asking about MOT renewal whilst on the road and out of the UK for more than 13 months (12 months new + max 1 month carried over from old MOT) which is the maximum an MOT can be valid for on a vehicle over 3 years old in The UK.
Back in 2010 if your travels took you through Spain you could get your vehicle MOT`d on British plates at a Spanish garage, you needed UNA ITV VOLUNTARIA which is valid for 2 years, I can`t see that this would have changed but you would need to check the most up to date information, stick on beam deflectors were NOT a fail point. ITV cost back then was 40€.
This would have to be accepted as MOT in all EU countries even the UK.
Just note in Espana they are really picky about self builds and some MOT stations will not accept them. How do I know, lived in Spain for 7 years, resorted to cassette type build and would slide it all out for the test.
Get it passed and put it back in again after.
Been back here for 4 years now they may have tightened it up even more, they hate anything with a different number plate. :-[