Which part of the interwar period? It's a twenty year timespan after all.
For the 1920s you can't really go wrong with Morris Oxford or the Austin 7. The latter is ideal for the whole period, they staggered on as cabs until after the end of the Second World War. Matchbox/Lledo make/ made both of them. There's a useful three pack of them. The beauty of the Austin 7 is that it was also licence built by BMW so handy for interwar Germany as well. IIRC they used them to put the wood and canvas shells for their mock training tank on BMW Dixie chassis.
Oxford diecasts do an Austin 7 as well if you can't find the older models but you should, they pop up with remarkable frequency second hand.
Ford made Model Ts in the UK so any Model T can be used.
Matchbox did a rather nice Talbot Van as well as its Morris counterpart.
Hardly common but certainly iconic, they also did a 4.5 litre Bentley.
Good start point is to look up the listings for Models of Yesteryear.
https://www.vintagebritishdiecasts.co.uk/yesteryears/modelsof.htmObviously there's a load more out there from other makers but that should get you started on a decent range of passenger and light commercial vehicles.