http://assets.dft.gov.uk/publicatio...t-belts-in-cars-and-dual-purpose-vehicles.pdf
Definition of first used here:
The Road Vehicles (Construction and Use) Regulations 1986
"(3) For the purpose of these Regulations, the date on which a motor vehicle is first used is—
(a)in the case of a vehicle not falling within sub-paragraph (b) and which is registered, the date on which it was registered; .
(b)in each of the following cases— .
(i)a vehicle which is being or has been used under a trade licence as defined in section 16 of the 1971 Act (otherwise than for the purposes of demonstration or testing or of being delivered from premises of the manufacturer by whom it was made or of a distributor of vehicles, or dealer in vehicles, to premises of a distributor of vehicles, dealer in vehicles or purchaser thereof or to premises of a person obtaining possession thereof under a hiring agreement or hire purchase agreement); .
(ii)a vehicle belonging, or which has belonged, to the Crown and which is or was used or appropriated for use for naval, military or air force purposes; .
(iii)a vehicle belonging, or which has belonged, to a visiting force or a headquarters or defence organisation to which in each case the Visiting Forces and International Headquarters (Application of Law) Order 1965 applies; .
(iv)a vehicle which has been used on roads outside Great Britain before being imported into Great Britain; and .
(v)a vehicle which has been used otherwise than on roads after being sold or supplied by retail and before being registered; .
the date of manufacture of the vehicle.
In sub-paragraph (b) (v) of this paragraph “sold or supplied by retail” means sold or supplied otherwise than to a person acquiring it solely for the purpose of resale or re-supply for a valuable consideration .
(4) The date of manufacture of a vehicle to which the Type Approval for Goods Vehicles Regulations apply shall be the date of manufacture described in regulation 2(4)(a) of those Regulations."
So that's clear as mud...personally I think I'd put belts in...