Word on @Gaz's favourite website is that they had no choice but to close, possibly because they had problems with delivering product to retailers? other than that i have no idea, but whatever it was, they are a big loss from the market
My take on this is that retailers had issues with Magnum's deliveries and pricing, which resulted in some retailers not stocking their products, which then resulted in a lack of outlets for them.
However, I was told by Mr Magnum, that there was another problem (which I feel I need not go into) with an unpaid debt to Magnum which caused the shut down.
Either way, it is a shame, but these things tend to happen in the world of pyro unfortunately.