Thanks gents for the insight.
I am copying the B+ schematic of the Tubesandmore kit because it has a negative feedback regulation and it is simple. With the filament A supply , the cheapo chinese LT1083 £4 kit is a no brainer, it is cheaper than buying all heatsink components etc separately and it can handle up to max 7.5A:
https://xtronic.org/circuit/circuit-...lators-lt1083/
It has two In4004 diodes doing excatly what you described during connecting and disconnecting the suppy.
I would use a 125mA fast fuse for the B+ output and 1A anti-surge slow fuse for the HT transformer primary. I could connect a properly rate NTC thermistor in the series with the primary of the transformer to tame the initial capacitor charging in-rush current when it is plugged in but i dont think it is necessary in this case.
Then i can get two cheapo analogue voltage meters as panel display.
with the box, i can either get a cheapo wooden box of varying sizes from the local art shop. In the past, i use transparent air tight plastic storage containers. they are cheap, strong and very easy to drill air vent holes. My isolation transformer was housed in such box with cable ties + cable gland compression junction nuts. They are transparent so any smoking component can be seen from outside.