Mike, I'v had but a few of these in the past. The thing is not to get wound up about it.
Wait till Monday and phone him up. If he wants to exchage the cheque for cash, give him the oportunity to do that.
If he starts evading you, send him a letter that you wish to be paid, say, within 7 days. If he still hasn't paid, send another letter saying you wish to be paid in 7 days and if payment not recieved you will take legal action forthwith without notice.
It's not a lot of money and a CCJ will hurt him a lot more than not paying you or even a few free dinners you may be able to screw out of him.