Do you have to go Thursday to Sunday? In my experience trying to get back from any long weekend type destination is always hardest/most expensive on a Sunday. Monday return might give more options with points.

Your other option is to bookmark a weekend, and wait until the days before when more availability might come up, but that will most likely mean a random destination and last minute accommodation scramble.

Edit: Also having recently been pricing up an Ibiza trip for august bank holiday (for the same reasons as yourself) I did note there were a few avios options available to there, around that time.