Another trick is to make all your employees "contractors", or keep them as a succession of short-term casuals. Then they don't count towards your total, and they aren't covered by the unfair dismissal laws anyway.
A bit of a long and torturous story this one... back in July, I was offered a similar position in Manchester, but there were various reasons why we didn't want to move back then - not least the fact that we'd bought a flat in Edinburgh exactly one week previously. Turning that offer down was one of the trickiest decisions I'd ever made. Anyway, the gamble paid off in the end, and I'm now very relieved and pleased.