Bit early yet I would think. They are ripe when they are yellow rather than green and smell beautiful. They will last on the tree for a fair length of time too.

I think they should be left to reach their full flavour before the frosts - about October. They should be a yellow colour when they are ripe.

Thank you Owdboggy and Cammomile for your replies. I thought it was later on, couldn't remember. I have a friend who is desperate to take them off my hands and we've agreed she can have the lot in return for my having a couple of jars of the produce! (gardening has not been kind to my hands and preparing quinces is a bit too much effort now!)