Right then, I've removed the remains of the old drive rivets and now know what size I need.
The hole diameters on the caravan side wall are 4.8mm. (accepts a 3/16" drill-bit perfectly, a 5mm drill-bit doesn't fit)
Judging by the remains of the old drive rivets it seems I need 6 new rivets of 4.8mm diameter with a shank length of 14mm and a head diameter of about 7 or 8mm.
I've now spent hours on the internet unsuccesfully.
I did find precisely the size I want in white but only if I buy 1,000. A common problem, either that or it's only in black or only in a bigger size.
I did try tool-supplies.co thanks Damien but they are 6mm dia with a 10mm head costing £25.00 plus postage for a pack of 50.
I've already had to pay nearly £50.00 for the replacement wheel arch and that was 2nd hand! now it seems I have to pay half as much again just to nail it to the van. (if I wanted black they would be less 1/4 the price)
I could drill everything out to a larger size but I'd rather keep it original and at least matching the other wheel arch.
I did suggest to one supplier that if he just sent me 6 in an envelope it could be sent as a sample with the added bonus that we wouldn't be wasting the other 994 and that he could feel so much more virtuous in this throw away wastefull society that we live in........didn't work sadly.
Anyone got any suggestions?
(4.8mm hole size, 14mm shank length approx, 7-8mm head dia, in white)