Hi Andy
Most of our commercial work is shops and so on and no contract is really needed.
We have a few larger commercial jobs - one is worth mabe £9000 pa and even for that we don't have a contract as such. We, and them, just go by the original quote.
We do the work, invoice them at the agreed interval, and they send a cheque.
Personnaly, I wouldn't worry about a contract as such. It's too complex.
Cheers