Claiming back VAT on van bought for business before VAT registration.

It's OK - I found it:

http://www.hmrc.gov.uk/vat/start/register/purchases-before.htm#1

Reclaiming VAT on goods you bought before registration
You can reclaim VAT on goods you bought or imported no more than four years before you were registered for VAT if all the following are true:

the goods were bought by you as the entity that is now registered for VAT (for example, the individual, business or organisation)
the goods are for your VAT taxable business purposes, which means they must relate to VAT taxable goods or services that you supply
the goods are still held by you or they have been used to make other goods you still hold
You can't reclaim VAT on any of these goods:

goods that you've completely used up before you registered for VAT (such as petrol, electricity or gas)
goods that you have already sold or supplied before being registered, or have used to make goods you have sold or supplied before being registered
goods that relate to supplies you make that are exempt from VAT
The word 'goods' includes goods that are intended for resale, and also goods that you keep as assets, such as computer systems, shop fittings, office equipment and furniture, tills, vans and other equipment. It also covers anything else you've bought that isn't a service, so it includes consumables such as stationery.