I wouldn't be surprised if some creative accounting has taken place and in a few months we're told that achieving 2% entails a cut.
Indeed
Prime Minister David Cameron has indicated the budgets for security services MI5, MI6 and GCHQ could be merged with military defense spending to ensure Britain continues to meet a key NATO spending target.
http://rt.com/uk/239621-intelligence-defence-budget-nato/
If you are wondering where the cuts will come, my money is on reservists. This will be done because
1) The Government doesn't have to sack any, it just has to not recruit them
2) Not gaining reservists sounds a lot better than sacking regulars*
3) Those reservists aren't going to get hired anyway; no-one wants the job, and when the Army were forced to come up with a forecast recruiting schedule for 2020, they shifted the bulk of the recruiting to start after 2015 to try to hid the fact that the recruitment drive was, and remains, an abject failure.
*Except that the regulars have already been sacked.