Anyone else had problems with parking sensors.

The ones on my Fabia 3 Estate work fine in the morning, but as the temperature warms up they fail.

Put the car into reverse the display comes on and the bleep sounds then after about 15 secs the display clears and a 5 secs bleep sounds.

The handbook says visit a specialist, that sounds expensive.

Sounds like it might be a failing sensor. Have a look on the VCDS section of the forum for someone local to you (there's a map on there) and see if you can visit them and get them to interrogate the parking aid ECU. I fairly sure it logs sensor faults and which sensor is faulty.