The paints arrived today - I found an online distributor in the UK, ordered by 9pm UK time on Tuesday and the delivery was just before 1pm today. Pretty good

Will be trying it out tonight. There are some spare bombs in my WNW Fee that will soon be brass!
edit:
Here goes - top row L to R: Mr Metal Chrome Silver: Brass; Copper.
Bottom row L to R: Humbrol Metalcote Polished Steel; Flat Aluminium; Gunmetal.

All of these are hand brushed, and buffed with the same brush once dry. I used clean, new brushes for each of the Mr Metal colours. I am quite impressed, the Mr Metal is no shinier than Metalcote, but Metalcote doesn't have brass nor copper - the Mr Metal is the best brass I have tried, and the copper is smoother than others. I have not used any thinner - the Metalcote could do with thinning, especially the steel. I am content with this trial, and will use the Mr Metal on my next build where required.