Write a contract for us

We have a requirement for a contract to be drafted which we will modify slowly over time. The contract will be between a web development agency and clients for weekly/monthly payments covering a set list of criteria (domain name renewals, domain hosting renewals, design etc) and will show a list of items not covered in the contract (print design work, print work etc). Must be written in accordance with UK laws. I expect that there is something generic available online, or a larger organisation will have something already that they can modify, so maximum spend on this is $40.