Garage consumer unit advice

[067256]

Called this morning to a ancient garage DB getting hot!! They have an ext lead with a tumble dryer and heater plugged in!!!
TT system.
2.5mm T+E supply to old mem switchfuse fed from conduit coming out of concrete floor.....don't know where the 2.5mm is fed from yet.
They want a new DB and new socket and light in garage.
If test results are ok can i fit a new 2 way DB onto the existing cable??
Just make sure i downgrade the supply cable( if i can find the other end) rcd protection to 20amp?
Any advice would be helpful
Thanks.

 

[Octopus]

Me thinks you need to find the "source" of supply and investigate a bit more as there are rather too many variables at this stage.