Can anyone help a newbie with fruit identification please?

Looks like a Bullace (wild plum) to me, fruit green/yellow rather like Greengage, makes a fantastic tangy jam.

Looks like a Bullace (wild plum) to me, fruit green/yellow rather like Greengage, makes a fantastic tangy jam.

Wild bullace are normally purple in colour like a large sloe or a small damson.

If they go a bright yellow they could be mirabelles.

We have a tree in a hedgerow with just the same fruits.  They are like tiny golden plums.  When they start to fall  badgers come and eat them and leave us piles of poo full of the stones .   

8doubles - I beg to differ

http://www.brickfieldspark.org/data/bullace.htm