This is "The Cave Children" which I made a good few years ago with Simon Farnaby (now of "Bunny and the Bull" Fame) and Tony Law and the Brothers Lamont, Remy and James, behind the scenes doing a good deal of the producing and technical heavy lifting.
Heads up: it's a bit "odd".
We did all the keyed scenes in a bedroom in the Lamont's house which we (by which I mean mainly they and art director supremo Josh Topp) spent a day painting blue, as you can see from these exclusive, candid, access all areas behind the scenes shots...
Dig the crazy strip lights gaffered to the wall. Health and safety my arse.
The whole thing cost about three hundred quid so Blair Witch eat your heart out.