Apart from the chocolate boxes joining the rfc under the floorboards and the visible corrosion on the cpc. Whats going on down here then? Thermal Damage? or just dirty on the cable to the right?

Looks like dirty cable to me.
Although its bad workmanship, it's probably been there for years and will probably continue to work for many more, like the thousands of other similar joints around the UK.
Looks like the cable to the right has been through the ceiling at some point, maybe in surface capping.
You can tell by the wire colours that its ancient.