Replacing the Air bags  Quite an easy job for a main suspension component. I'd already got one bag from Marcel Leisure. I ordered a second one. Free delivery, and it arrived at work within 24 hours - all ready for the weekend.   The main issue was the size of fittings, so I'll give a detailed parts list at the end. The bags are Firestone and have UNC and UNF bolts and NPT air connection. I'd only managed to find a UK source for the bags two months earlier - rather more convenient than arranging a delivery from the USA, and at £105 incl VAT and delivery I was very pleased. NPT fittings came form an Amazon supplier strangely. And UNC and UNF bolts from Southam Agricultural supplies:      New bag and piston assembly      Bottom view      All the bits and pieces     Fitted and inflated.      Fittings in place       The parts