Wonder how many people don't realise that the Wago MF boxes only officially comply (as MF boxes) if they are secured via their 'button' or screwed to a joist...
Suprisingly, seems that Hager still do a 701 junction box that is like the old ones I was thinking about.
I've seen one original in a loft simlar that was black and in VIR (fortunately had been disconnected) but used a similar system - so it's been around for a good while...
And did one odd house a while back that had been wired with large metal junction boxes and some sort of plug socket arrangement with flexes labelled to switch, light, fan etc. New builds done by a farmer so used some system more common in industrial I think. Did make for fairly easy isolation of wiring though!