Does anyone have a sample of such a contract? Basically it should stipulate what I must do, and very importantly, the client.

'Cause despite the fact that the guy is a lawyer, he was completely amazed that if he failed to produce the content, he's going to be billed for the contract amount.

Secondly, as this guy is an old client, he gets a reduced rate from me - but he's been delaying payment.

I know he's good for it, but would I be a complete bastard in saying in the normal hourly rate is his hourly rate + 20%, and the account is settled within 7 days, his normal hourly rate applies?

7 days is a bit steep to up the price, I think 14 is more reasonable, with 7 days payment stipulated on invoices then you can send him a warning letter after a week. There is something you can join in the UK which is very usefull for about 100, but I forget.. anyway found thishttp://www.sessions.edu/career_center/design_tools/freelance_templates/index.asp

My suggestion is if he is an old client thats slow to pay tell him that really you would like payment up front as its how most of your other clients now pay.