Ready-made Semaphore Signals top poll

The round steel post used by the GWR from the 1930s onwards was not much different from the tubular posts adopted by the other companies around the same time. Looking at photos, the main differences seem to be in the way that the GWR designed and fitted brackets compared to the others.

The lattice masts seem to have been used most in the highlands of Scotland and in a few other areas.

As David points out the GWR had lower quadrant and they did use tube, but it was not very similar to the LMS/BR type.
I think this is where the market will run into difficulties, Lattice post were quite widespread depending on what railway company built the original signalling. Think East Anglia, the GN main line from Kings Cross northbound, the LSWR used lattice posts as did the LMS. LNWR were often square post wooden and there were other company varieties too. Because of this variation to make an 'authentic' model signal would determine which company/region the signal would be used in. I think that those who would pay say £25 for a single arm starter, (using the mentioned viessman as a comparable price/quality indicator), would be the sort of modellers or enthusiast who would want the signal to be 'correct'. I don't mean exact fidelity, but to be a very good representation of the signal for that region/company.
For example a model of a GWR branch line with lattice post signals would be as wrong as a GN branch with GWR lower quadrant signals, and I think that those likely to pay for quality signals would likely recognise that anachronism.

If I'm right, that unfortunately potentially fragments the market and drives up costs further.

http://greengoscalerail.fotopic.net/p31919529.html
Heres an example. This is a simple LMS lattice post bracket signal. It is very different from an LNER version. Having built it, I do think that when you start to get this sort of structure, which were pretty common in the UK, good quality RTR signals are going to be a very expensive proposition altogether. Having said that I'd love to be proved wrong!