Thanks very much for your replies guys - very helpful indeed.
I think these must be fruit flies right enough - i had no idea we even got fruit flies int he uk, so i have learned something new today.
I must have the wrong mix and need some more brown material in the bin i will get on this today as i have lots and lots of junk mail that needs shredded.
As for airing i haven't done this as yet - the main reason the flies so will do this at some point today or this week.
Need to go and buy a bag of soil so i can stick a layer over too.
Thank you again for your replies it has made me realise i must be doing something wrong.
ShazM