If the UK is in debt,
The UK national debt is the total amount of money the British government owes to the private sector and other purchasers of UK gilts.
UK public sector net debt in February 2012 was £988.7 billion, equivalent to 63.0% per cent of GDP- (note this excludes financial sector intervention.)
Source: (Office National Statistics publications page updated March 20th, 2012)
If all financial sector intervention is included (e.g. Royal Bank of Scotland, Lloyds), the Net debt was £2311.6 billion (147.3 per cent of GDP.