McAero,
The Conservative policies are pretty much outlined here - £2.7 bn increase, with £1.6 from reorganisation within the MoD (DLO merger, etc, etc) and £1.1 bn from savings made elsewhere and allocated to defence (See Bunter's recent RUSI speech). This all presupposes that the James review savings targets would be met, though...
Labour policy seems to be steady as she goes, although Buff is, by all accounts, likely to be replaced as he wants to do something else. Of course, we should be due an unanticipated defence cutbac...sorry, restructuring process about two years in.
Lib Dem policy has been discussed somewhere on the Army means... In essence, though, policy seems to be:
1. No replacement for Trident
2. Cancel Eurofighter and use all that money elsewhere (someone's not been paying attention nor heard of the phrase 'cancellation clause'....)
3. Er.... can we get back to you on that, please?