We have just moved back to the UK after 10 years in Cayman. DCs 4 & 7 were born there and apart from holidays in the UK had never known anything else. We thought moving from there to a city would be a bit much for them so we looked at market towns which have enough going on without being too big and busy. We also looked at transport links so we could get to a big city for days out. You get more for your money up north rather than in the south, depends on likelihood of where you will find work of course. For teenagers you need to think about how they will get around i.e. trains or buses to the cinema & shops etc, plus of course high school.
As Special said 5 years is a way off and things change but if you are looking at shipping would recommend Sta-Mar and of course don't bother with electrical stuff as won't work here.
It is significantly cheaper to live here even with income tax. Utilities and groceries are much, much cheaper than in Cayman.
We have settled in well and have no regrets about moving back. If you have more questions just ask and also try the British Expat Forum (another website, not an area of Mumsnet) as there is loads of practical stuff on there from the threads people post. Locrating is another good site for schools in the area you want to research.
Things to consider are not having a credit score so getting credit cards, phone contract and mortgage may not happen right away. We are renting for a year and have pay as you go phones. We had to pay 6 months rent in advance so need to factor that into your plans.
Have you spent much time in the UK? Perhaps family holidays for the next few years could be spent here visiting areas you think you might want to live in i.e. not touristy areas. Do you have family & friends here already? that might narrow it down too.
I'll come back if I can think of anything else.