Thanks Mark. I decided to go out and set up under the clouds and try it once again. With the forks pointed East I got an almost immediate lock. So I turned the scope off, pointed the scope south as I usually do, and turned it on. It locked almost immediately again. Given all of the trouble I've had since I mounted up on the wedge, I'm thinking of going out and buying a lottery ticket tonight!
No doubt this was an aberration, and I'll follow your advice when it fails to lock next time round.