The year of Colin's car is relevant. If the car is vintage the water pump was slightly changed late 20's to suit the later high radiator (1928/9).
The club do have the machined casings for these cars - these are expensive (£550) but do allow a solution as the impeller, shaft and bearings can be sourced (though not original) or these replicated from original samples which can be provided. The top spout will require an additional collar to suit the taller rad.
The problem with any surviving original vintage pumps, after 80+ years, is corrosion (that curse of the AC engine). Sometimes these pumps can be repaired though, but you first have to find one (they are as rare as hens teeth).
Rod does not have any camshaft-driven vintage water pumps, but he has the PVT, and later, belt-driven ones which are very different. Robin is very likely the same, but I'll let him answer. If Colin has a used original one then it's back to checking corrosion/porosity.
