Bradclark and Xabba are spot on, it's the fact that for the first time in ages Europe is pretty much at peace, aside from terrorist strikes which you can't really fight properly with a standard organised military, Europe has nothing to worry about, Russia is rattling its sabre but hasn't tried reforming the USSR yet, Germany isn't suddenly building up a military machine, France isn't readying a large navy to take over the seas. To the average Joe in the streets, Iran and North Korea are the other side of the world and thus not a threat to mainland UK. The NHS is sucking in funds and creating MRSA, most of central England is a lake, and there's corruption and scandal wherever you turn...
Now imagine that Brown announces he's going to put more money into the military by taking funding from something like...I dunno, public transport, or the multi-million pound draining NHS, can you imagine the headlines? The press would have a field day, and heads would roll quicker than you can say 're-election', just look at all the hoo-haa created over the Trident Replacement scheme. If the threat is not on the doorstep, Britain won't arm itself against it, as I said once before in a post about the new Astute class, we can make excellant machinery, you only have to look at the Astute and Type 45 to realise that...but we only do so under pressure, and since the end of the Cold War, that pressure has evapourated. People just don't see any threat any more.
Just because a threat isn't visible...doesn't mean it's not there, or won't rear its ugly head in the future, that's a fact that many people out there on the street or in the government don't seem to realise.
If the world was a more peaceful place then I'd be the first to advocate disarmament...but the world isn't any more peaceful today than it was fifty years ago, and as a saying goes...those who beat their swords into ploughshares shall be ruled by those who don't...
