Thanks all, some things to consider for sure.
We'll be getting them a tutor as they have been taught from day one in Catalan, so they are certainly behind with their written English. Although I dont have concerns about them being accidemically behind - the curriculum here seems to be slightly more advaced than the UK. They are definatly covering subjects that I didnt do til high school and friends back home say the science for example is way ahead of what their kids do. How these classes will be delivered will be different so using the learing support centre at the school will be a given. We'll support them as much as we can educationally.
implantsandaDyson Yikes! This is the kinda of thing im concerned about. The shows you mention, in my mind are adult shows, cant imagine allowing him to watch them just yet 
Also, he's so far not be allowed to game on line. And Ive steered away from fornight. He can, unchecked, become obsessive. So I can imagine him being totally sucked into it, abandoning other interests.
Looks like I might have to loosen the reigns on this one!
He's a huge Minecraft fan (again I have to steer him away from this occaionally if hes abondoning other interests) The school he's going to has a MC after school club, so he'll probably be interested in that.
He has in the past done breakdancing classes and he was really quite good. So we'll look into that for him. Not 'Street Dance' though - "ITS NOT THE SAME THING MUM - DUR" 
He plays FiFa on the playstation, but cant kick a ball to save his life. I think he'd probably enjoy drama etc. Something he not had opportunity to do here.
He and his brother are very close and watch/enjoy the same things, (except Dr Who!) so its never really been possible for him to watch slightly older stuff, he hasnt been bothered by this so far. I'll think about them having seperate TV times so he can maybe get stuck into some different shows.
The youngest will be very into the idea of scouts/forrest school. And he's certaily more sporty. I think he'd benefit from team games/competition, again not something he's experienced here.
They both would like to learn an instrument. The eldest plays a little guitar. Im sure they'll get the opportunity to try this out at school.
Im more than happy to have a house full of the kids friends (sucker!) so will encourage that. And we are hoping to get a dog that they have been asking for for years.
I think we'll take on the extra curriculars slowly, the move and new school will be exhauting for them i'm sure.
We'll contine to encourage them to explore and express their emotions. They've always been quite open like this, so hopefully that will continue. Puberty sneeking in has meant the eldest has been a bit out of sorts with his emotions, but hes been pretty good so far in saying he feels a bit weird and doesnt know why, a little tearful at times. But im being gentle with him and allowing him his own space when he needs it.
Arrgggh, I suppose im probably over thinking a lot of things, and they'll be fine in the long run. Its been a quick decision & obviously we'd have prefared more time to prepare, but it is what it is. We'll all have to adjust.
@flitwit99 North Wales/Northwest Boarder, any good to you?
Which has reminded me I should checkout Mumsnet Local. Ive been quite isolated here really, so im looking forward to meeting some new friends myself.
@SunshineSpring good luck! Scary isn't it!
Thanks again everyone. My mind is a little more at ease.