I have a company and so was looking into doing it through that, when I get the projects finished and more than a couple of them on the road at a time. Admiral multi car was pants for my needs - I was insured as the only driver and the premium went up massively each car I added, even though I could only ever be using one at a time! Now I just insure a couple and swap the insurance every couple of months when I want to drive another - paying the admin fee to change each time seems to work out cheapest for me at the moment if I limit what I use when.
For you chaps that already have trader's policies do you find you get stopped by the police a lot to go through the paperwork? Now with ANPR cameras and the new law just in saying it is illegal to own a car that is not insured (unless it is SORNd) then I can see myself getting stopped a lot and a load of paperwork sent to me threatening fines unless I have a policy that covers each specific licence plate?