The Plague of Flies

My latest attempt to grow my own produce is going a bit wrong. Last year I managed to grow tomatoes, peppers, courgettes, and chillis on my patio, which was pretty successful overall, so I decided to make a start on some other stuff this year - and as it's too early to plant anything outside, I thought I'd try growing some mushrooms. I bought one of those kits from the garden centre whereby you put some compost in a polystyrene box and water it for 10 days, then add some other stuff to it, and then get mushrooms in around 2-3 weeks. So far so good, but the first part of it has to be kept in warm, dark, conditions for optimum effect. So I put it in my airing cupboard.

What I hadn't realised was that there must have been some fly eggs or something in it, as the box seems to be spewing forth tiny black flies that are beginning to escape into the house. I've been trying to keep them at bay by going into it every so often and squashing all the ones I can see with a bit of loo roll, but I don't think it's the answer. Later on this week I can move the box somewhere cooler, but still not sure what to do with it as it can't really go outside unless I get a mini-greenhouse to protect it from the frost. But I don't want a plague of flies in my house! What should I do? Should I give up the whole thing and chuck it away? Or should I keep going? I've also put up some fly paper in the airing cupboard so will see how many it catches over the next couple of days, but I might have to give in and just buy my mushrooms from the shops. Seemed like a good idea at the time though. Will definitely do the tomatoes and chillis again this summer, and of course there's the apple tree which might bear fruit if I'm lucky! It's like the "Good Life"!