Thought I'd update. After thinking long and hard,checking out a few alternatives I decided on a Vucube 2. I searched the web for the best supply only deal,which was £675 if memory serves me right. Then there's fitting.... I'm not the smallest of chaps and to be honest,drilling into the roof didn't float my boat. The Caravan was going in for its 3rd service so asked what they would charge. 2 to 3 hours labour, they had only done one before on a motor home. They matched the price I could get and didn't charge extra for the roof mount kit (£25)
It's a doddle to use. One press of the button on a very small,neat control box and in a couple of minutes your picture perfect.
There are a couple of downsides, the Dome is black, God knows why. I did see on eBay a white one advertised but a call to Maxview said they only come black.
The Vucube 2 is a twin LNB unit, and this is where I made an error. I assumed it comes with 2 leads into the Van, not correct. 1 lead,one blanking screw on the Dome. Not a problem to me but if your having one fitted,make sure you specify what you require. For me, well worth the money.