I'm not sure i'd pay out for a service after only 3000 miles, even if it is 12 months old. If you're getting rid of it, I doubt it will give the vehicle any added value, even more so if you end up doing a PX with a dealer against a motorhome.
I've purchased several used cars from main dealers that have been 'between' service schedules, and they don't service as part of any deals.
By the way, as a Motorhome owner myself, and a previous T5 Camper user, I can say you won't regret the change if you do buy one.