buyer would like it posted, which is fine for me.
If it was fine to post it, why didn't you list it with posting as an option? It may have reached a much better price.
Items listed for collection often sell very cheaply because the number of interested buyers living locally is so much smaller than when postage is offered. I've had some great bargains that way!
Not all buyers are cheeky enough to ask for items to be posted. Others will respect your decision to sell it for collection only, so you lose out on what may have been higher bids.