Hi Chris, at £120 I presume they are buying OE props. Why not try an aftermarket prop at nearer a third of the cost.
I wanted a lesser pitch prop to increase the RPM on a 15hp Mercury EFI, I was quoted £160 for an OE prop. I bought an aftermarket prop of the same pitch and size from SSI Marine (
https://ssimarine.co.uk) for £48. Great quality, I couldn't tell the difference between the OE prop and the aftermarket prop, and the pitch was exactly what I was after.