If anything I think it might have further weakened Britishness simply because it's reinvigorated the identity debate and national navel-gazing.  As Brits we don't know who we are, and the sight of Boris wearing a Cross of St George lapel badge, Beckham kicking a football, and a warbling Leona Lewis with a double-decker bus pootling about, hasn't exactly filled me with pride.  Cringing embarassment maybe, but pride no.

The problem with Britishness is that the more you discuss it the more apparent it becomes that it doesn't actually exist, or if it does it is indefinable and meaningless.  It is the sum of England, Scotland, Wales and (Northern) Ireland, and until the Britishness-mongers recognise that inconvenient fact instead of offering up Britishness in opposition to the national identities of the British Isles they are on a hiding to nothing. 

It's amusing that Martin seems to believe that this outbreak of Hooray Henryism will be a phenomenon that will last beyond the wet week that any sensible person without an agenda would see to be the reality of the situation. British and Britishness are concepts of identity that are in terminal decline. The achievements of the athletes in China has been beyond even optimistic estimations. Kudos to them. But in all seriousness it is delusional to think there is any political significance in these achievements.

I think you're right that the government and its successor (presumably, led by David Cameron) will try to use Team GB's Olympic success and the 2012 Olympics to stir up British patriotism / nationalism and thwart the drive towards a Scottish independence referendum. However, I think you're quite wrong in saying Salmond's celebration of Chris Hoy was 'jarring': a great many people in Scotland and much of the media there are keen to follow and celebrate the success of Scotland's Olympians - as are, by the way, many English, Welsh and N. Irish people with respect to their Olympic athletes. (The case of N. Ireland is a particularly double-edged one, as the province isn't even acknowledged in the name of Team GB, which is partly because N. Irish athletes are entitled to compete for the Republic of Ireland instead.)

It's actually also true that Scottish visitors to China for the Games - whether athletes or spectators - weren't allowed to bring in the Saltire; similarly, English visitors had any illicit Flags of St. George they wished to bring in confiscated. All of which was doubtless connected with Chinese internal politics relative to Tibet.

Iain Martin's view, while having some merit in relation to how politicians might wish to portray and manipulate the Olympics, is completely out of kilter with how Scots have been reacting to all these manifestations of so-called 'pride in Great Britain'. They see all of this as an essentially English phenonomen: another example of English people using 'Britain' as a trope for England and wanting to appropriate the achievements of Scotland; in this case, those of its athletes. I don't completely agree with this perception of it; seeing it more as political and media manipulation to whip up pro-British sentiment primarily on the part of the English - a practice of which Iain Martin's piece is itself a prime example. But the reality is that this Establishment view is out of keeping with the way Scots (and, increasingly, the other nations of the UK) perceive what is meant by Great Britain: something aggressive and anglocentric (Scottish perception); something aggressively England-denying (English perception); something that conveniently leaves N. Ireland out of the narrative (leaving many in the Province to draw their own conclusions about their future in whatever Union may survive).

Particularly ironic, then, that it was the National Anthem of Great Britain - played as the anthem of Northern Ireland - that was booed at the Scotland / N. Ireland match. Perhaps, in fact, a reaction against all the nauseating Britain Britain Britain rubbish the Olympics have given the media another occasion to shoot off about.