None of the money for defence is "new". It's a re-announcement of the cash requested by MoD from the Treasury contingency funds as part of the operational estimates for hot, sandy places and the Balkans. The £900m for equipment is largely for UORs.
Main Building will have to stump up a 50% share of whatever UORs receive final approval two years or so down the line. Usual Neue Arbeit spin and bo**ocks. All equipment bought reverts to MoD's core budget for depreciation and other beancounter niff-naff reasons after an agreed period, further eating into the dwindling kitty.