Greengrass, any good degree. A 2.1 is good but a 2.2 and a broad set of interests and skills can offset the lower degree.
A history or international relations degree would be suitable for Intelligence as would a science degree - analysis.
A science degree would be an asset if going for logistics.
Many Cranwell graduates have BEng.
Many Admin types have LLB.
Languages can be very useful for many tours later on.