I thought so too particularly with:

1. Ensuring that voltage drop along L and N was less than 4% of supply voltage at maximum design current of the ring final circuit at the furthest most socket to the RCD/RCBO.

2. achieving below a maximum earth loop impedance to guarantee the required trip performance of the RCD or RCBO.

I have never seen a stated limit on the cable length, only on area.

As there is no stated limit on volume, in theory you could have a ten story house with a footprint of 100m2 and wire all ten rooms sockets all on one ring main(!).

Hopefully Adam will be along to comment further.....