Adding the 'standard taxi-time allowance' to a civil logbook is not permitted for CAA licence issue purposes. The CAA will allow 5% of total military time, but no more than 10 hours for CPL issue; no allowance is stated for PPL issue. See Appendix B to Section A of LASORS 2008 'Recording of Military Flying Times – Taxi-time allowances'.
However, if a student has faithfully logged all his/her military flights in a civil personal flying logbook in accordance with civil requirements, then that is a different matter.
Going back through all the auth sheets to extract the take-off and landing times for each and every trip, then working out the 'off chocks' and 'on chocks' times is a complete and utter PITA and frankly not worth the effort.