I can only comment when selling our house in the U.K.
Our estate yes, had ‘sole agency’, but they did not have the ‘sole right to sell’ – in the situation of if we sold it privately, via the internet etc.
Check the agreement – if it is only ‘sole agency’ without the ‘sole right to sell’ clause in there as well, I would just knock them on the head.
If you have a buyer you have found yourself, just leave the agent out of the loop.
Let him try and sue you!! As a purchaser owed 100,000 pounds for a building not built in Spain, and unable to get my money back from the developer without a huge lengthy process via court, don’t think this estate agent would worry me.
Out of interest a) how long have you been with them and b)have they actually shown anyone round yet??