Marktime Pay on Commissioning from the ranks.
I cannot confirm the policy of pay changes during the war but I did experience the effect later. I was commissioned in 1964 after 6 years service as an NCO Radio Observer and subsequently Pilot. On appointment to Plt Off my basic Sgt pay (which was higher than a Plt Off) was retained until promotion to Fq Off. My flying pay immediately increased as did my marriage allowance on moving to the officer's mess.
The system was termed "marktime pay rates" and gave those who experienced the result a considerable increase in pay when compared to the normal rates earned by officers with Direct Commissions.
I suspect that other pruners of that period will have a similar story.