Good point, that is why you ideally want them to put something in writing, be it text or AW message what service you want and are they going to do it, this then forms the basis for a contract, irrespective of the clause for "my time" as a new contract and terms has been agreed upon and supersedes the former.
This would then give you the the legal capacity to take it further.
But for £100, as said before, is it worth all the hassle. No.
You just have to check the reviews, and more importantly on here. If you TOFTT with a WG with no feedback/reviews then good luck.