According to the Guardian, the total is £4,983 billion, more than half of which is the value of people's homes. The total includes personal, commercial and public assets such as vehicles and machiney, financial assets and intangibles such as the value of patents. I'm not quite sure which category Marmite comes in - the article quotes a spokesman for the British Tourist Authority saying:

"We've also got fantastic towns and cities. London is renowned as a fashion capital, with some of the world's leading designers, and a lot of people come here for shopping, because of brand names such as Selfridges and even Marmite."

Instead of the Marmite we could get 2.516 billion pints of bitter (at £1.98 a pint) or 14.655 billion 4-finger Kit Kat bars at 34p each.

Kitty