Blood and Custard

"Why use Halfords paints when Railmatch do aerosols as well as jars of paint."

Because Halford's aerosols are half the price, twice as large and don't clog as badly. The only 'hobby' aerosols which are any good are the Games Workshop ones but their range was already sadly limited before they did away with their matt varnish. That said I can't recommend them highly enough if you want black or white.

I also find that the Humbrol aerosols clog and become unusable long before they are empty. I have spent the time with fine wire and soaking the heads in different thinners but with very limited success. For individual vehicles I generally brush paint then spray varnish - with a quality brush the 'grain' effect isn't too pronounced for the varnish to remove it and on timber vehicles it can be what is required anyway. I don't fancy it on a rake of coaches however.

You can get propellant for the airbrush without having to use camping gaz canisters, probably buy them from halfords cheap, they're the type used to power those hand held air horns and such like.
Crimson and cream is one of those liveries which seems to be a pig to get right, as you say bachmann and hornby differ slightly, the worst ones for different colours were probably lima as i have a few of theirs and there are 2 distinctly different shades of red.
I can't honestly think of a colour off the top of my head that might be close to the crimson but i was thinking of one of the older austin rover colours for the cream, montegos and such like ran 2 colours which may be close one was originally classed as white but was a bit creamy and the other was sort of beige/cream. If halfords don't have a good colour then try one of the other car paint types eg carplan or holts. The holts ones had an adjustable spray pattern nozzle too but may be difficult to find. It may be a good idea to try your local independant car parts shop as they tend to keep stock longer than halfords.
Good luck anyway and let us know if you find a good match.

In reply to Jwealleans enquiry about the "camping gas" I used to run the airbrush with, I did this because the airbrush propellant in my local model shop cost around £5 for a 500ml can and with all the re-sprays I was doing it was getting a bit expensive to buy but I just couldn't bring myself to part with £100 or so on a compressor so while on the lookout for cheaper thinners one day in Wilkinson I saw some camping gas cans and thought at £1.99 a pop I had nothing to loose in seeing if it would fit the airbrush hose. Got it home and guess what it fit perfectly and on reading the ingredients list found that it was composed of the same two gases, namely propane and butane the only difference seems to be that camping gas has a similar odour added to it to natural gas, which I didn't find a problem as I don't have a spray booth so all my spraying is done outside on fine summer days. You can't get more well ventilated than outside. On the thinning side it's no different than using the proper gas, I've also found a paint supplier that sells cans of thinners at really attractive prices.

In reply to Jwealleans enquiry about the "camping gas" I used to run the airbrush with, I did this because the airbrush propellant in my local model shop cost around £5 for a 500ml can and with all the re-sprays I was doing it was getting a bit expensive to buy but I just couldn't bring myself to part with £100 or so on a compressor so while on the lookout for cheaper thinners one day in Wilkinson I saw some camping gas cans and thought at £1.99 a pop for 750ml I had nothing to loose in seeing if it would fit the airbrush hose. Got it home and guess what it fit perfectly and on reading the ingredients list found that it was composed of the same two gases, namely propane and butane the only difference seems to be that camping gas has a similar odour added to it to natural gas, which I didn't find a problem as I don't have a spray booth so all my spraying is done outside on fine summer days. You can't get more well ventilated than outside. On the thinning side it's no different than using the proper gas, I've also found a paint supplier that sells cans of thinners at really attractive prices.