I had the same problem of flies before. However I read an article saying
that kitchen stuff attracts flies and suggest covering a layer of brown
stuff (I used shredded junk mails and newspaper) and moist the layer. The
situation has improved a lot then.

CK

"Martin Sykes" wrote in message
...
I've got three compost bins and only the one which is currently in use has
the problem with flies. The other two have none at all. I think it's down
to
having a lot of fruit added to it. The other two have mostly garden
clippings in them.