Apologies tazcat, but I was looking at it with a legal eagle's eyes.
Advertising at law is called an 'offer to treat'. Any response to that is an 'offer to buy', and acceptance of the offer to buy then makes a contract for sale.
So yeah, you didn't offer to sell, but made an offer inviting an offer to buy!
Sorry if that's confusing, but that's what legal crap can be like. After 40 years in the work place, it's a bit hard to let your mind settle back to everyday thinking!
Even though I'm now retired, I still often help out friends and acquaintances with issues they have with insurers and debt recovery agents, at no fee. Haven't lost once with those, so far !