WHere are you buying the car from?
If a dealer, ask to see theres.
If getting finance (HP) the HP provider will do one before they buy it, so ask to see theirs.
However, neither of these give you any guarantee, I *think* if you get one through the AA and it turns out to be wrong, then you have some recourse.
Lets be honest, if you have to pay £15 on the purchase of a car which is £2k, to make sure it is straight (well as straight as a Hp check can tell you) then it is money well spent.
How can the text check service tell you what the VIN should be, if it is on finance, ever been written off, reg plate changes, engine changes, colour changes etc?
This is one of the circumstances where paying a bit more will give you a whole lot more peace of mind.
When you get you copy of the HPI check, tke it with you to view the car and make sure that the VIN number matches the one on the HPI check - look at the VIN under the windscreen and also on the engine bay, just to be sure.
And tell the seller you will do this, if they get a little jumpy about it or ttry and stop you from doing it then walk away.