Hot tub supply

[littlespark]

Depending on the requirements of the actual hot tub, the cable size should be adaquate, but it is likely sitting in the attic as a flat grey twin and earth cable.
If you were to extend this to outside, you would need to use something appropriate for outside, as twin and earth can not be used externally.

We still need the electrical requirements of the hot tub to advise fully.

 

[PS Electrics]

Not sure we are getting the full picture here!

The photo of the 2way consumer unit is NOT an RCD but you mention one to the right of it?
I also suspect another CU as a 2way (6 & 16A mcb's) doesn't seem sufficient for storage heaters! or whole house, (ie where are your cooker, ring finals and lighting connected?)

From what the OP said, my understanding is there is a Consumer Unit with fuses that supplies this board so this is where all the house circuits will be. The concern seems to be about not running a new cable front to back of house. If the cable is of the correct size and tests out ok then that should not be a problem. The OP will need a new House Consumer Unit but seems to be aware of that.

Do NOT get confused with the incorrectly labelled Main Switch as others have said it is NOT an RCD and by look of it the shower install was non-compliant as it wasn't RCD protected!

Most likely the shower was a 16th Edition install, if it was it would have been compliant at the time. Probably going to need a new sub board though as Newlec is Newy & Eyre which badged manufacturers products. This being an Electrium (Wylex) MCB which now look obsolete unless you source the secondhand market. This is on the assumption a smaller size MCB will be required.

Can you step back a bit and take a photo of the whole consumer unit(s) set up, including meter if indoors.

This would be helpful just to be 100% on what is actually there.