Good thinking there, Batman!
Yes, I have split a ring into two radial circuits quite often. The cable used for a ring (2.5 sq. mm) can also normally be used on a radial circuit (U.S. style) with an OCPD of 20A. (The exception would be if the cable has to be highly derated due to ambient temperature or cable grouping, which isn't normally a problem in residential work.)
The main thing to watch is where a radial created out of a ring feeds a kitchen/utility area, keeping in mind that most homes here have the washer, dishwasher, dryer, etc. on the ring. In those cases I would want to add dedicated circuits for the major appliances (I prefer to do that anyway).
The IEE Regs. on rings have changed very little over the years, but specified radial arrangements seem to alter with almost every new edition.
The current arrangements are
here.
