I need a marketing letter writing

I would like a marketing letter writing to send to around 200 restaurants, selling maintenance contracts for Gas Appliances, such as Boilers, Gas Fires, Commercial Catering, etc. The package I am selling is similar to British Gas's 'Homecare' plan, where a monthly fee/contract is paid for repairs, servicing & certification to Gas appliances in the UK. There is no deadline for this. One page would suffice as long as it covers everything and doesn't sound too cheesy. I will add the logo/company info myself, all I need is a page of marketing text. My company is a family owned private supplier of mechanical facilities services - specializing in Natural Gas & Liquid Petroleum Gas services. I don't want to lie to my customers - I want them to know that i can supply the same service that they are already getting but for cheaper and at a higher quality.

If you would like to send me a proposal for this project, please attach an example of works which you have already completed.

I would prefer it if the writer has some knowledge of marketing in Gas/Construction/Engineering services, although this is not a necessary.