GrantT I have a politics degree so I kind of know where you are coming from. I have to agree with Pontius Navigator and also drawing on tucumseh's points. However, I think you might actually struggle to write 5,000 words on this subject alone partly because there's only so much you can write without loosing your way in the whole essay especially as a non-expert in the subject. I know I would have had trouble. For example, I did an essay looking at how successful technology was during the first Gulf War, and got more or less everything in there with 2,000-2,500 words, if I recall. That was quite a big topic to cover that could have warranted 5,000+ words, or even a novel, if I'd given a full historical account of the war before diving into the technology side. That wasn't the point of the essay though to do that.
Personally if I was doing it, which I'm not, thankfully, I'd look at some of the programmes in general in recent years, and abandon trying to assess capability gaps in any great detail. At least you'd be able to ask more simple questions and draw conclusions as to whether there were/are options to save money (like buying off-the-shelf) or why these programmes are seen as so important, looking at the kind of political and industrial pressures to carry them out even if it has resulted in rising costs and affected delivery schedules. In this case, there's load of stuff. FRES instantly springs to mind where money has been spent but nothing bought whatsoever. The Lynx Wildcat and the chopping of the rotary-wing budget when British forces have needed more transport helicopters for years. Nimrod MRA4 of course is in there. The CVF programme is an intriguing saga from both political and industrial perspectives. Same with the Eurofighter and the A400M, particularly the political. The Chinook HC3 debacle. You are already using NAO material and there's also Commons Defence Select Committee reports on equipment procurement that make interesting reading.