Everybody needs a Renault 4. On that basis, like the 2cv it doesn't count as a part of your list. The Beetle (I just checked the rules) is banned. It doesn't say why, but you're not allowed a VW Beetle or a Talbot Tagora.
We can, however, allow the Austin 1300 GT as a spare (or a spare spare) , although I think it the slightly common and flashy cousin in the family. Vinyl C-pillars are just too much. Although the rumour is that it would have been the Austin 1300 Cooper if commission negotiations had worked, I still think it slightly naff in the form it was produced in. I'd prefer to limit you to a 1968 MG 1300 two-door in a muted shade of pale blue or grey. That seems closer to the ADO16 philosophy than the socially ambitious Austin.
Otherwise your extensive list of one car is fine, although the Cortina is a mistake.