Daimler. 2.5 V8

[Dude3000]

Hello, I was wondering if anyone could diagnose this issue on a Daimler 2.5 V8
(Sell it had occurred).
Positive earthed.
New points, new rotor arm (rebuilt distributor), new dynamo, new control box, new leads, plugs.
Battery went flat (also new) after waiting for some seats, that took 3 months to refurbish; charged battery.
Car chugs away from rest, okish at speed but very lethargic, no petrol on carb over flows (experienced that problem in another car when floats dropped in carb pots), put new high octane unleaded in case old petrol syndrome, no overheating, no mayo in radiator,
One thing is that the lights in the dials literally disappear when stationary obviously get better when moving, but although
the dials lights were never great, completely dark is an issue. The amp meter goes off the scale when moving off.
I think it is an electrical problem, but open to any "I had that, or your Dynamo is duff, or the belt is not tightened enough...
Earthing?
I even wondered if it was just sooted up, as it does few miles, and those are to a garage to get more stuff fixed.... So took it
for a decent run but made no difference.
Any ideas - hugely appreciated
David