Hi Adam,
As Ray says "everything comes down to a compromise".
You have already said that you want it to be "Not too heavy..." which straight away steers you away from one sector of the marketplace. We went to a show a few years ago with a plan of buying a continental van such as Knaus or Hymer and couldn't find a single one we could tow safely at the time.
In days gone by you could have looked across the field to a new Carlite or Van Royce and known that you were looking at quality, but it would have had a very big price tag and and it would have weighed in the heavyweight division. But those makes are gone anyway for new purchasers.
You said you were interested in the "best make of UK caravan". Well after the recent downturn there are not so many mainstream UK manufacturers left. Off the top of my head I can think of only Bailey, Swift (inc. the Sterling and Sprite brands), Elddis and Lunar as the big production line players; with smaller manufacturers such as Coachman, Bessacar, Vanmaster and Freedom offering their more hand-built offerings. (Have I missed somebody important anybody?) You will find that all of the major manufacturers have lots of very satisfied customers and all of them will have a small group of customers who will say "never again". The smaller manufacturers probably have a higher percentage of satisfied customers for their vans, but you will pay for that and they are by no means immune from critics.
My strong suggestion is that you take a day to have a look around the stands at the NEC Show in October and it will give you a very good opportunity to compare the feel of almost everything on the UK market. We went there last year to buy a Bailey.... spent most of the afternoon agonising over a Lunar... and bought a dealer special version of a Swift.
The other thing I would suggest to you is that much more than buying a car, say, the dealer you purchase from can make a huge difference to your eventual satisfaction. A good dealer will make the whole process of buying an enjoyable and rewarding experience; they will pick up on some faults from the factory that you will never know about; they will respond to your aftercare problems in a positive and helpful way. Bad dealers regularly fall down on these things. If you browse around these pages you will pick up on some of these dealers that have good reputations.
Happy buying, I envy you the excitement that we will not have again for another few years.
Cheers
Mike A