The PM mentioned a freeze in recruitment of MOD civil servants as a starter. Although the headline 5% looks like the armed forces are bottom of the heap, with the consolidated £1,000 it's 7% at £50K and a shade under 8.4% at £30k. A 5% rise in MOD personnel costs based on 2021/22 would be £670 million.
£13.4 billion Service and civilian personnel costs in 2021/22.
This is nominally unchanged from the previous year and represents 29% of defence expenditure, down from 32% in 2020/21.
Source - MOD Departmental Resources: 2022 (ONS)