Your advertisement will appear for four weeks the weekend after your cheque is cashed. No rubber cheques please, if for whatever reason your cheque cannot be cashed, your advert will be binned. If at this point doubts have been raised in your mind about the trustworthiness of this method, I can understand. I also have the same doubts when sending people money for services, indeed I will not use my credit card on the internet. Remember, each cheque transaction is registered and can be traced so any problems can be sorted out quickly.
Money orders are less so but they still carry reference numbers.
Indeed if you want to advertise anything else your quite welcome, just remember five pounds per item. Advertise your item to the whole world.