Aubergine doctor required urgently

My aubergines always end up with the fruit rotting as soon as it appears from the flower.  The plants are healthy and flower perfectly and then it all starts going wrong.  They are in a greenhouse.  Please help as this is the third year of trying and always the same problem occurs.  Where oh where am I going wrong?

Like tomatoes, you can have non or poor polination problems. When the plants flower tap them gently to loosen the pollen. Lots of bees are handy but you can't always bank on them being around at the right time My greenhouse has a couple of Ceanothus  planted by the door and the bees seem to love them and I always find a few of them busy in the greenhouse.

Had the same problems last year in the greenhouse,the aubs were in there with cucs ,toms and chillies.Eventually I took the aubs and the toms outside and the were fine after ,the formed fruit and were ok,but lost a few weeks.I blamed the cuc.....cross pollination I am not sure....but separate everything was fine.This year I have keep the aubs separate and the are doing great,I do not know if this is just chance but that was the conclusion I came to...would love to hear expert advice.
Aubergine