Who to believe

Garden Gate

My caravan is due for its first annual service. The dealer wants almost £400. They told me it must be done by someone who has NCC accreditation. When I mentioned a mobile operator (not by name) they said that would not be in line with the warranty. On contacting
the guy had had in mind (who is Caravan Club accredited) I saw the NCC symbol on his website. He assures if he services my 'van it will be in line with the warranty. Who do believe? His charges are almost half those of the dealers.