If you just search for Europa it shows all variants - including the more modern SE
105 Twin Cams and Specials
22 S2's
And 138 "Europa" which could be any variant.
That's 255 in total.
I believe the models on the Registration document were used as written on the registration applications by the dealers at the time, and could possibly have been truncated by the inputter when moved to the computerised system.
Also if you click on the Special which shows 53 licensed vehicles (I believe this means taxed, including the free Historic classification which they should pretty much all be covered by), it also shows that in Q1 of 2019 there were 49 taxed and 29 SORN'd vehicles.
I agree there aren't many left whatever of these numbers you choose to use, but then they only made 9947 total production of all Europas from 1966 to 1975, compared with around 387,000 MGB roadsters and nearly 126,000 MGB GT's over their production run.
Edit May 25,2020. Corrected typo.