My diagram is basic and I actually only need one of the three options with two 2-gang outlets. The radial is near the midpoint of the ring so the resistance around each led back to the MCB should be similar.

It can be done in a way that is safe and regs compliant, but it needs a bit of thought. It also falls into the category of things that might worry folk whose idea of design is to see if there is an example in the On Site Guide - the same folk who think a centre fed radial is two circuits and wonder how to test it...

Practical issues not all fittings and back boxes work well with 4mm cables so if you need 2 lots of 4mm and some 2.5mm  in the same back box/ terminals it may get a bit tight.

As you note , well centred on the ring it is not an issue, as the current split down the two 2.5mm legs is fair. However, if it was a heavily loaded branch near one end it might be worth thinking harder, though of course spurred from the MCB direct it would  be fine.

When things are non-standard It is worth leaving a plan in an envelope near the consumer unit for future use, so that whoever has to do some inspect and test in the future is not confused by it. I know nobody does leave notes, but it is a good idea.

Mike.

The way you have drawn the diagram, shows that having a ring final circuit in such a formation is pointless.

Wiring it as a radial final circuit using 4 sq.mm. cable also shows why the spur is perfectly acceptable.

Thanks, the layout of the outlets favours the ring final configuration I think but I know people often prefer the radial one

Thanks Mike, a full wiring schematic will be left but let's hope others keep it updated :-)

Looks OK to me, but as Mike points out, the terminals may not accept all of the cable. BS 1363 accessories need only accommodate 8 mm², but some (e.g. MK) accept 12 mm².

the layout of the real outlets, not the diagram that is

This could be a candidate for MK LOGIC RAPID FIX with 2x 2.5mm and a 4mm 

How is the current split across the two legs of the ring?

Why not just extend the ring?

The current is reasonably well split.

I'll look at extending the ring but don't know as easy and I'm keen to know what's possible, what's frowned on and what's a no-no.