What size armoured cable for greenhouse electrics?

I don't think you should use a RCD type socket like that if it's already on a circuit coming from a CU with RCD protection.

 

It only acts as a secondary barrier, JWK, and whether or not a CU has RCD protection is not a problem and in fact it would react a mill-second before the CU RCD.

 

Any power sources for domestic appliances should be routed on a separate circuit so that one failure does not affect another.

You're not likely to have a fridge in a Green House, Scrungee, although, granted you might have it in a Garden Shed but, again, they should be on separate circuits.

 

Well, not really, if you plan it right, Scrungee. If a person wants to buy electrical items to do so and buys the normal, common sense items then it's very unlikely that an Electrician would turn their nose up to them.
Alright, in this case, Shep maybe hasn't consulted with the Electrician but he seems to have his head "screwed on" and isn't going to buy an indoor light switch or the like for the job in hand. But, planned right, you would find that the Electrician would be more than agreeable to a person buying the needed items if he knew what they were.

 

It's a legal requirement to do so, @ARMANDII , he should have given you a signed off Part P Certificate too.

 

I'm still a qualified professionally electrician, JWK, even though not practicing. That allows me to legally still carry out electrical work. I only asked my friend to check my work as I did it under one man circumstances and there were times when I was tired. So it was just as a reassurance to myself that I had him check my work.

 

You'll still need the certificate Armandii, you can self certify if you have the Part P qualification, your local council will tell you the correct route, don't risk a fine.

I only know this since I put in a new CU myself for my extension including new outside circuits. I borrowed all the test equipment from work but even though I work on aircraft systems me nor any of my colleagues were certified for domestic installations. So the council sent around their inspector who tested and signed off my work, better to be safe than sorry with electrics.

 

It was all done, JWK, even before I called in my friend to double check it. I think what I was trying to say, badly, was that I was able to carry out the electrical work and certificate it myself with the approval of my Council. I worked with my Council on the planning and building of the concrete base and also the final height of the Observatory so that I didn't contravene any building or electrical regulations. I also had a request from two of the Councillors to inspect the Observatory and the work done. They arrived and spent all the time peering through the Telescope, operating the Shutter, turning the roof around and telling me that they like the garden, without even referring to the work done, apart from agreeing that it had been a lot of work and saying "Well done"

 

Not the best way to check the circuit breakers, Harry!!