Courgette Failing Fruit

Some of the fruit on my courgettes are going yellow at the ends and appear small and wrinkly.  They are doing this at about 5cm long and not filling out.
My courgettes are in the greenhouse in pots. The first time i've done this as I usually grow them outdoors but couldn't keep the slugs  off them.
They are watered evenly and the greenhouse is fairly well aired.
Any ideas?

Are they being pollinated,  if the insects are not getting in then you will need to do this yourself, if not the plant will not set fruits.

I usually have to hand-pollinate mine even though they're grown outdoors, and the chances of successful insect pollination indoors are even less.

I've had a few courgettes already and a few more are on the way but have now got another problem - my 2 surviving plants have 8 female flowers open and looking for lurvv, but the males have apparently disappeared off down town to welcome/ogle Jessica Ennis back to Sheffield! 

The embryonic fruit will appear to set, the flower shrivel, and then start to grow even if it's not been pollinated - however even if pollinated they can suffer from a type of blossom end rot (different from that which affects tomatoes) if the remains of the petals remain attached to the fruit for too long in damp conditions, but don't remove the flower until it knocks off quite easily (molegrips definitely not required!)

I usually have to hand-pollinate mine even though they're grown outdoors, and the chances of successful insect pollination indoors are even less.

I've had a few courgettes already and a few more are on the way but have now got another problem - my 2 surviving plants have 8 female flowers open and looking for lurvv, but the males have apparently disappeared off down town to welcome/ogle Jessica Ennis back to Sheffield! 

I have the same problem, loads of female flowers and virtually no male flowers and if there is a male flower its not open at the same time as the female ones and my courgettes are rotting off as they haven't been pollinated.

Can you hand pollinate the female flower without having to transfer the pollen from a male flower?

I remember been told years ago that to hand polinate you can remove a male flower and stuff it inside a female flower and tickle 

The fun I have been having this year is courgettes and pumpkin deciding to only produce one sex of flowers at a time!

there are moments when you sit back, stare at the plants and wonder if they do this for fun.
The trick one of my friends does is to grow as many plant as possible, with the theory that one of them will remember to produce a male flower at some point!
And if that doesn't work she gives up and stir fries the excess flowers that wont be pollinated!

My sister, who's growing courgettes in Italy, is having a similar problem- the little courgettes shrivel and die. They can't be pollinated, since they start shrivelling before the flower opens; the flower stays small and closed.
Never had that problem... Her courgettes are watered and fed regularly, weather there has been unfailingly warm, what else could be wrong?