Thanks.
I think I have got it covered. I have it in
writing after some "negotiation" (in fairness the dealer put his hands up straight away), that it is to be collected by the local H-D dealer, and the gearbox is to be thoroughly inspected for damage. If it's ok, they will fit the primary vent kit. All this will be paid for by the selling dealer (Charles Hurst). In the event the gearbox is damaged I can reject the bike and get a full refund for the total sale price of the bike.
I haven't considered what Charles Hurst will do if the gearbox proves to be damaged and I reject it. They will have to get it fixed unless they want to sell the bike with the fault. Not my problem then though.
The salesman from Charles Hurst has been really good all the way along....credit where credit's due. He admitted it was his fault from the off.