Dealer has been out and it seems this is not the first one to leak. I have spoken to the dealer who informed me that that they will speak to Elddis to see if it will be repaired under the warranty. I have now written to the dealer to inform them my purchase was from them not Elddis and they have the duty to repair not the manufacturer.
I wanted to raise the issue so other owners can check their vans before they leak, as you say this one may have been poorly fitted but on both sides of the van?
It's only by posting on forums like this that an individual can get to the bigger, picture if one exists.