When researching a UK Motor Vehicle there are a number of useful sites, such as CarVeto or CarAnalytics, which can be used to locate details which may help you to understand more about the vehicle.
Not only do these types of site confirm the vehicles Make and Model type, they generally will also show when it was First Registered, the date of the Last Change Of Ownership, which is when the last V5 (log book) was issued, and when the M.O.T. & Car Tax run out, or has ran out etc.
Sometimes you may research a vehicle and it may come back as having been Registered but the Make & Model type, the V5, M.O.T. & Car Tax details are all blank, which may indicate that it is now on a different Registration Number. Whilst at other times you may research a vehicle, with is currently Taxed but has never had an M.O.T., despite being more than three years old, which may indicate that it is exempt under the Road Traffic Act from requiring an M.O.T., which may indicate that it is a Police Vehicle.
Sites such as CarVeto or CarAnalytics also include details of a Vehicles M.O.T. History, showing when an M.O.T. was issued, if the Vehicle Passed or Failed its M.O.T., the vehicles mileage at the time, and any Advisory Notices about the vehicles condition.
At the site operated by the Motor Insurers' Bureau, under certain circumstances, you can check for free to see if a UK vehicle is currently insured, or not.
And don't forget to search the registration number, with and without space and all appropriate search engines, which may locate details of it being advertised for sale etc, or listed on sties such like PistonHeads or Rate-Driver, which may give additional useful details or the vehicles use. It is also worth search the registration within Facebook, which may identify posts in which it is listed.