Morganic there is a guy who I see regularly in the fields at the back of my house, he shoots rabbits. I got talking to him one day when I was under my van greasing it. He told me he worked for a caravan dealer for many years shifting caravans between sites, collecting from customers etc, he also told me when the dealer in question got busy he used to service a few as well-this worried me a bit.
I service my own van, as a ex mechanic I feel confident in doing it and it really isn't that difficult. I also have the gas side of the van serviced when I have my LPG central heating done annually, this does not cost any extra as the heating engineer says there is not that much to check.
I'm sure all dealers are not the same but I think it pays to make sure you are getting value for money and a proper job done.
Good luck