Business sales terms and conditions writing

I need a terms and conditions of sales writing for my business

We sell used machinery and I am concerned as the business is growing and acquiring more customers, I believe it would be sensible to add some terms to the purchase.

I would expect this be no longer than 1 page that would go along with any invoice and we deal with 3 main categories of client, direct to consumers, export clients, and business to business sales, so may need slightly different approaches for each client.

I would prefer someone who is qualified in this area of UK law and I have taken my price from PPH suggested guidelines, if it is to cost more to get the best outcome please just let me know.

Thanks
Ryan