So I heeded Stavros' advice and used the triple qx grey primer, eurocarparts own brand and a Halfords top coat (not appliance gloss white) and all it tickerty boo. I had to remove all paint before re-prime ring though as the triple qx primer reacted with the Halfords paint left on the hull. I've also changed stand design, following other advice on here so it is just st a baseboard with rails either side of the keel and under the bilge keels. It's less elegant than other stands but has worked for me. I'll try to take a pic later.
I'd be surprised if it's 'cos you're using too much paint. I left mine for weeks if not months with the Halfords primer and had the same issue. Even with 'stavros' ' primer I've still not had the heart to try the d stand!
Phil