What on earth did they do with the money?
It doesn't cost GBP4.5M to design and manufacture wireless light switches and the associated backend systems.
Off the top of my head I would say a team of 5 competent people (1xelectronic, 1xmechanical, 2xsoftware, 1xmanglement) could do it in a year without too many long days. Manufacturing setup and tooling for the plastics would be less than GBP200K plus GBP50K for testing. Say about GBP 500K for the lot. I'm not including marketing or production costs because they would be covered by the actual orders. If they have a backlog of orders then they don't need to spend a lot on marketing etc.
I'm sorry, but it sounds like they wasted the bulk of the money on things other than actually designing product.