Everyone knows the original Volkswagen, the Type 1, as the Beetle but was this ever it's official name, the name the factory gave it? A lot of VWs are listed as 1300 or 1200, but if we don't know which engine size it is (I can't tell them apart myself) is it correct to put Beetle in the model field?

I think that first models did not even carry a model name, they were just "Volkswagen".
1200/1300/etc. came later.
Other names were mostly nicknames.

Beetle was never an official name, nor any of the other nicknames. It was first used by the New York Post in 1938 in an article describing the new car.

Before the war ended the car was officially known as the Kraft-durch-Freude-Wagen (KdF-Wagen), even though the VW symbol was also in use since 1938.
After the war the name Volkswagen was established as the brand name and first new models built from 1946 on (production in 1945 was from spare parts) were known as the Standard . In 1949 the better equipped version Export was added.

These names were used until 1961. From then on numbers depicting the engine size (1200; 1300 from 1965; 1500 from 1966) were used, while until 1965 the additional word Export was kept for the better equipped cars. In 1972 the larger 1302 and in 1974 the 1303 were added.

All the names known are just nicknames and vary from country to country. The English Wikipedia entry lists quite a few of them: http://en.wikipedia.org/wiki/Volkswagen_Beetle

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For us this means any extra nickname should be written in inverted kommas, e.g. 'Beetle' or 'Käfer'.

or 'Coccinelle'

If the exact model (1200, 1300 etc) can't be found, do we list them as Volkswagen 'Beetle' [Typ 1] or simply Volkwagen [Typ 1]?

I'd say that we should use the nickname used in the country where the scene was made, but if it is not known or not easy to find then we can just keep model name empty for these.

I think the 'Standard' to which Alexander refers was officially known as the 'Typ 11' and the Export as 'Typ 31'. As a young lad I remember my Uncle Maurice visiting us; he was with the Allied Control Commission in Germany after the 1939-45 unpleasantness. I had never seen a Volkswagen, of course, and was fascinated when he produced what I think was a driver's handbook covering both models. This would date from the Ivan Hurst era, before Heinz Nordhoff was appointed.
BTW I'm not suggesting for a moment that all the pre-1949 Typ 1s on the site should be altered; I just thought it might be of interest.

typ 31 is the sedan/fastback typ 3

There was a 'Typ 51', the first of which was built in August 25, 1945 and was produced in around 1300 units until January 29, 1946. The production of the 'Typ 11' in high numbers occurs in 1946: in March the Major Ivan Hirst team starts a rhythm of 1000 per month. This 'Typ 11' remains the sole type produced until June 1949. By then, the factory was already under the direction of Heinz Nordhoff, that took charge on 1st January 1948.
The Export model was introduced in July 1949 and, by that time, the designations go as follows: Typ 11A ( Standard ); Typ 11B ( Standard r.h.d. ); Typ 11C ( Export - sometimes also called Deluxe ); Typ 11D ( Export r.h.d. ); Typ 14A ( Cabriolet Hebmüller ); Typ 15A ( Cabriolet Karmann ) and Typ 15B ( Cabriolet Karmann r.h.d. ).
About chris40 Uncle's car, it would be interesting to know more details. Could you remember some of its details, Chris? For instance, if it was l.h.d. or r.h.d., the trim and other details that you find of interest.

No, I'm sorry: he didn't have the car, just the handbook! His ‘company car’ was a Citroën TA of some description (which he wrote off, he claimed because someone had fitted it with crossply tyres). I’m sorry I can’t remember more but this must have been nearly sixty years ago.

Thank you for your answer, anyway! I'm always curious about these period stories and their details.

In the US, I thought it was:
Typ1=Sedan, Typ2=Station Wagon, Campmobile, Squareback,Fastback, Karmann Ghia Coupe/Convertible
using this as an example: http://www.thesamba.com/vw/archives/lit/70fullline2.php

Then in 71, the Fastback was the Type3 and then the Super Beetle added to the Sedan.

Then in 73, it's the Basic Beetle and Super Beetle.

Here's what I'm using as a reference: http://www.thesamba.com/vw/archives/lit/type1_2.php