Bjorn you can get some comparisons from this converter chart.
http://www.e-paint.co.uk/Colour_alternatives.asp
Start by choosing colour range BS381C then choose BS499 there are close alternatives but the RAL number is down the scale a bit.
I use BS single pack polyurethane mat paint from http://www.rainbow-paints.co.uk/ (Bournemouth) Maybe they are happy to ship a litre or two?