Hello Iain and welcome to Eribafolk.
I'm gussing that because it's a Puck it's pre 2010 so you'll not need to go to an Eriba Dealership although for the time being I think that Jandi are still in business. They are due to retire but they're recognised as one of the best dealers and certainly the most knowledgeable dealers in the UK.
Jean and Sandy. Give them a call:- http://www.eribacaravans.co.uk/

Many folk with older vans use a Mobile Caravan Engineer and we recommend you look at this list to find someone in your area. Mobile Caravan Engineers

On the subject of annual servicing there is some debate as to whether it's necessary to have the van serviced every year of perhaps every other year. It obviously depends on how far you travel every year and the conditions in which you store it.

Randa