You can register for VAT voluntarily (even when below the aforementioned threshold). Many businesses do, for many reasons, especially if they sell things on top of providing services. I.E. to claim VAT back on purchases you have to be VAT registered, so if you're selling goods, it sometimes makes sense to voluntarily register for VAT so you can claim the VAT back on the purchase price. This is especially true when a company is dealing exclusively with business and private sector customers (who can themselves claim the VAT back).
You'll know if he is VAT registered, as he has to give you a VAT invoice with a valid VAT number. See here: http://www.legislation.gov.uk/uksi/1995/2518/part/III/made
If he's VAT registered, he's paying VAT! (or will be facing the consequences of not doing so).