score:5
The process was pretty gradual. For the WRNS, their association's website outlines it. Post-WWII, the service shrank to about 3,000 women in support and administrative jobs. Wrens had never been allowed to serve on board ships. In 1974, it was decided that integration had to happen, but this took decades:
The transition process was long enough to give plenty of time for retraining.
The WRAC association website is less detailed, I'll keep looking.
The WRAF seems to have been more integrated with the RAF from its foundation in 1949, with about 80% of trades open to women from the beginning. The first female aircrew were in 1962, and training was fully integrated by 1970. Operational female aircrew happened in 1990, and the services merged in 1994. Again, there was plenty of time for retraining.
Medical staff were special cases. Female medical, dental and veterinary officers always had full commissions in the men's services. Chaplains were another special case, complicated by different religions' rules on female ministers. Each of the British services also has an associated nursing organisation, whose personnel are mostly female.