War is wasteful
When there is an actual shooting war, it's amazing how much equipment goes to waste. If not destroyed by the enemy, the squaddies will put paid to it.
So I'm with Lewis on the "buy overseas" approach. Right now the UK has a war on its hands, and the goal should be to end it (preferably in victory) at the lowest cost in lives and treasure. That puts a priority on generous quantities of proven, low-cost equipment - not much of it will come back from Afghanistan whether the UK wins or loses.
Newly developed weapons are not going to make it out there in time to affect the outcome of the war - although the arms companies are using the war to justify development of new technologies.
It was George Orwell who said that the British always prepare for the last war. It does seem that too much effort is going into preparation for large-scale conventional wars (that is, apart from the small scale of the UK forces).
BTW I used to work in the tech side of the arms industry, and it is fun to work on military technology... but in our case (South Africa) it was the cheap and cheerful stuff that made the difference in the field.