dave dont be fooled b&q's paint match service is not what it actually says.

it wont match any colour 100% as it doesnt mix its own quantities from the scanned colour. you know in the painting seciton of b&q there is that display of colour charts with all the shading scales of said colours, well what the b&q system does is matches the scanned colour with whatever it has closest on those colour charts as there all scanned into the system, and its happened to me twice over the last few house where it picks a colour and the scanned colour is in between 2 shades on the chart, it picks one, but the other colour ends up being better suited, once they've scanned the image for the colour match they'll tell you what the shade and colour is called then grab the chat to make sure your happy.

but as i've said its not really a paint match service it just saves you looking through those colour chart slips to find the coloset match

hope this helps, well it doesnt actually help with your application as you require an aerosol application, but jsut thought i would say.