Hi Alisdair – I suspect given the number you've quoted that your scheme is based on the default scheme – so you'd be talking about something based on para 58 in the schedule to the default scheme. Obviously DCLG don't update the default scheme itself so you'd need to track through the amendments to the equivalent provision on the PR regs – which is Schedule 1 – Part 6 – Para 25.
HBINFOs own consolidation of the PR regs get you as far as 2014
http://new.hbinfo.org/legislation/main-regulations/ctrse-pr-schedule-1#part6
which gives you the version of para 25 that 2017/204 Sched 1 para 8 ( that's the one you're quoting, I think) amends.
