And you used to be able to book the initial FI skill test in the same way but, according to the Examiner's Handbook, that's all changed
2.5.3 All CPL Skill Tests and Instrument Rating Skill Tests plus all FI and Examiner AoC are to be arranged through FCS Test Bookings. The CAA reserves the right to allocate a particular CAA Staff Examiner or Training Inspector to any applicant's test/check flight as it thinks fit
I assume all of your initial FI tests are allocated by Flight Test Bookings??