This morning's Public Sector Finances report informs that the UK is currently £645.3 billion in debt in September 2008 (i.e. before the latest round of partial nationalisations).
That's pretty much £10,755 per person in the UK (based on a round 60m population).
If Wales were to start from scratch financially tomorrow, then based on the Oxford Economics Foundation report published in July on our own debt (itself based on the UK's own profligate spending on war etc.) , it would take us almost 70 years of independence to build up that £645.3 bn level of debt.