The case of the electric shower trip..
The consumer unit turned out to be a 60 amp 4 way plastic Wylex with plug in mcbs.
Shower cable appears to be 6mm all the way back to the CU.
Tails are 16mm and I note some conductors have been snipped to suit incoming terminals.
6 amp lighting.32 amp ring main (cable looked oversize for 2.5mm)
Cooker cable disconnected, no mention of immersion heater.
32 amp shower radial. (potentially 39.5 amp 9.5kW load)The cooker is fed from the ring and has some sort of built in selector switching restricting total load.
Space heating is also from ring main!
I forgot about checking the immersion and didn't have time to look behind boxing for bonding, sorry:-)
I think the system is fully loaded. Changing the consumer unit/upgrading the tails sounds a bit professional to me?
It is possible the immersion is fed from other unmarked CUs but the whole set up is very confusing; three flats plus some off peak stuff.
regards