I hadn't realised that Hornby PLC was involved - they bought out Airfix in 2006, Corgi in 2008 and, now, 25% of Warlord with an option to buy a majority share in the future.
This, actually, may have had an impact on Warlord concentrating on a few core games and expanding it's international footprint - sales of the heavily franchised Dr.Who and 2000AD ranges would never have brought in the profits (even if sales hadn't fluctuated) of their other games.
I don't think it's got a lot to do with Bolt Action sales - Warlord has been expanding its markets so sales have remained fairly consistent, even accounting for the GW practice of re-releasing the books for a new version! I think it's to do with creating a global Warlord Games brand, getting known globally for those games and building their market share in other countries rather than just the UK. They're following the Games Workshop model - GW used to produce dozens of smaller, spinoff wargames and boardgames but discarded most of them to concentrate the GW brand on WHFB/WH40K.