I was under the impression that the regs required 20amps of ccc for the RFC reg to apply. I'm sure it would be fine in practise.
If it's allowed then your way is obviously simpler and better!
The only regulation that I know of specific to the RFC is 433.1.204 which covers the case of the OCPD being above the cable rating, but due to the ring structure with fused sockets along it, that is acceptable.
However, I interpreted that as saying you can use an OCPD of 1.5 times the CCC for such a RFC, not that you must use 30A fuse/32A MCB and not anything less. After all, it shows examples of the same BS1363 accessories on a 20A radial in the appendix.
Now one of the main arguments for the RFC is the greater coverage and application of diversity that comes from having 32A backing a number of sockets, versus the 20A radial (or 16A radial more common in the EU), but I never though it was obligatory.
Without wanting to kick off yet another "RFC versus Radial" argument I would still stick with the RFC as I like both the ability to check end-end via r1,r2,rN readings, and the redundancy in the CPC against a single open (which would not be spotted, unlike an open live on a radial). And here I would feel the 20A versus two radials at 16A (which is actually above 2.5mm CCC under method 103!) gives better diversity of socket use.
Maybe the "20A RFC" should be the topic of another thread!