Here in the states we can actually get house flies on line- I don't know about in the UK- Blue bottle's are my favorite - the larva keep longer in the fridge- and they are pretty easy to dust - and where I get them sells "fly food" I was told by a member that i should be gutloading before feeding them- which I'm sure is true I've been trying new things as far as that goes- I get them from a place that sells supplies for keeping Mantis -