I quite like the OE plastic containers on our cars

They melt. The windscreen reservoir one the MMC sent me in 2003 did so and I had to switch back to the earlier and smaller pre-1988 reservoir which I must keep at least semi-full or it suffers the same fate.
I have been meaning to get around to it for the last 24 years and this thread will push me.. As for the coolant overflow tank, Rover used safer metal, painted black. Luddite must have one on his Morgan. However, they are small and canted. The Mulberry thingie (above) keeps the fluid level.
... it only takes a quick nosey in the tank to establish all is well.
I want to avoid that. The coolant tanks are often filled with hyper-heated coolant!. Your last picture in your earlier past shows an exterior level indicator which would be great (see below). I could fit one anywhere I choose to my existing expansion tank. I would then get a matching reservoir for windscreen fluid.
Lorne
![[Linked Image]](http://www.gomog.com/TEMP/ExpansionTankWithLevelIndicator.jpg)