Looking at the first picture, there is a grey sheathed cable going from the left of the meter position to over the top of the cutout and disappears. What's that?

Also the main DNO cable seems to be propped up by a lump of rotting wood, is that the case?

And is that insulating tape just above the head? Does it provide adequate mechanical protection?

I notice that despite the head being upside down, the cover is the right way up. 

Due to the cable and equipment belonging to the DNO, if you have any concerns, get in touch with them.

Edit; I have often seen tar coming out the bottom of main heads. Not sure whether this has any. But having it upside down might make a right mess of the fuse carriers and connections

Looking at the first picture, there is a grey sheathed cable going from the left of the meter position to over the top of the cutout and disappears. What's that?

Also the main DNO cable seems to be propped up by a lump of rotting wood, is that the case?

And is that insulating tape just above the head? Does it provide adequate mechanical protection?

I notice that despite the head being upside down, the cover is the right way up. 

Due to the cable and equipment belonging to the DNO, if you have any concerns, get in touch with them.

Edit; I have often seen tar coming out the bottom of main heads. Not sure whether this has any. But having it upside down might make a right mess of the fuse carriers and connections

I do believe that is the main earthing conductor from the service cable, it looks like it enters in the top but then one line returns. Then it terminates into the MET.

You could be right with the rotten wood, I have a second incoming supply at the same property with similar rotten wood and signs of damp! 

I'm planning on getting the DNO on site to go over the installation, it seems there's been multiple additions over the years.

You can just about make out what's happening.