As a Yank I don't see what you Brits are complaining about. Any US programme of this type would easily cost 10-50 times as much.
And let's look at the results. For that billion swords (over twelve years), roughly 10% of the drones have suffered unscheduled dis-assembly and are lost. The rest are presumably still flying around. Okay, their actual combat experience is quite limited, but they do appear to be simple surveillance drones and are basically meant to surveil locally, methinks. ;-/
If you are a government setting up the kernel of a huge future fleet of Eyes in the Sky, using a new tech, you will expect teething issues and new models that fix problems encountered in early rounds. A new tech with a ten percent attrition rate over twelve years is not that ugly, and is in fact barely adequate for acquiring decent failure data!
I'd have guessed at a considerably higher failure rate myself...