It all depends on your budget. Usually you will get more van for your bucks from the European manufactuers, however, because they are often viewed with suspicion over here, they can sometimes be difficult to trade on. If however, you are buying from a dealer in that make, then usually no problem. However, as mentioned they are supplied to full UK specifications and so you need have no fears on that score. EU vans can range from the cheap end of the market right through to the very top end, as mentioned by Hymers etc. Adria make excellent vans and have a big dealer network here and so do have a look at them.
Spares are always an issue with any van. Just look at the comments on this Forum regarding some so called classy UK vans. As fashions seem to change every year getting even small parts can be a struggle, although obviously the UK market has more availability.
We have a EU van with the door on the 'correct side' for us as we use it in Europe most of the time. It was a cheapie but the fittings are superior to more expensive UK vans and it tows far better. It does not have an oven, which is as we like it. We have more storage space.
As far as bunk models are concerend I suspect you will find more choice in the EU market as they like those types of vans. The UK does do them but are more limited. Also 5 and 6 berth vans here are often pretty heavy, or even worse, have very low payloads and cannot reeally accomodate all the people they are designed for. Kids require a lot of kit. The EU models are more 'child friendly' in as such they do not have fitted carpets and so are easier to keep clean. They also have less 'twiddly bits' which are better with children.
Go to one of the big Shows and have a look at what is available before making your mind up. Then visit the dealerships for the models you like and really try the van out to ensure it is what you want.