Hi Yvonne,
Welcome to the forum. It's not too clear what you are asking. Are you the vendor, the purchaser or an intermediary between a vendor and a purchaser? it's the solicitors who decide the exchange of contracts date, and any one who wants to exchange for £100 with a 10 week completion sounds to me that he wants to use the £100 as an option fee, and write a purchase contract for he "and assigns" which means he is going to sell on the property to a third party at a higher option fee. Just a guess, and nothing wrong with this transaction, other than if the option holder doesn't find a buyer, he'll not complete and lose his option fee (£100 big deal) and it'll cost the seller a lot more than that in waiting time and mortgage interest in the meantime.
