Mainly British makes, "Sit up and beg" Fords..Anglias/Poplars/Prefects, Vauxhalls, Morris, Wolseley, Riley, Baby Fords aka Model Y. Older 30's and 40's cars might be still on the road in the 50's.
More upmarket cars might be used by the better off, Ford V8 Pilots.
Smattering of continental cars, Fiats/Renault etc. and very small numbers of cars of American outline, Chevrolets, etc.
(Bulleid had a Chevy Bel Air as a company car)
VW Beetles and the VW van (Kombi to Aussies/Kiwis) used by the ESB and the P & T.
Farmers sometimes used small Fordson or Thames dropside trucks for bringing animals to market or churns to the creamery but the number of vehicles on the road would be tiny compared to today. Small businesses; shops, bakeries, etc. might use the panel van versions of the above for deliveries.
Most people used bicycles and younger lads bought a motorbike before graduating to a car.
In country areas, the grey Fergie 20 would have to feature even though a lot of work was still carried out by horses.
CIE still used drays and carthorses well into the 60's for local deliveries.