On 29/08/2019 10:15, Theo wrote:
Graham Nye wrote:

What's the feed to the CU? ...

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed. I'll see if I can find out
what the MCB on the other end is.

80 A is an unusually high rating for a domestic MCB. Are you sure it is a
MCB? Could it be either a main switch or a RCB with an 80 A rating?

If you're not sure, take a clear picture of it, share it somewhere
(e.g. imgur.com) and post a link here.

Checking the source end of the feed would definitely be useful.

What protective device(s), if any, are on the radial circuit feeding
your existing pair of double sockets?


--
Graham Nye
news(a)thenyes.org.uk