WW - Thanks from me too. Something was nagging me after I made my post and you identified it. However, given a pension of £25,000, additional gross earnings of £17,475 are still only £13,695 net of 20% tax (£2,550) and NIC (£1,230) before you enter the 40% tax bracket at £42,475.
If my reckoning below is correct, a salary of £40k on top of a pension of £25,000 will only gain you an additional £23.5k after paying tax and NIC.
Gross pension = £25,000
Tax on pension = £3,505
Net pension = £21,495
Gross salary = £40,000
Gross income = £65,000
Tax on gross income = £16,010
NIC on gross salary = £3,933
Total tax and NIC = £19,943
Total net income = £45,057
Total net income above net pension = £23,562 (i.e. take home pay)
I did the same sums for a salary of £50k to see if the results were consistent:
Gross pension = £25,000
Tax on pension = £3,505
Net pension = £21,495
Gross salary = £50,000
Gross income = £75,000
Tax on gross income = £20,010
NIC on gross salary = £4,381
Total tax and NIC = £24,391
Total net income = £50,609
Total net income above net pension = £29,114 (i.e. take home pay)
I'm no expert so please feel free to check my sums. Income tax calculator
here. NIC calculator
here.
If I'm right, even a salary of £50k will only be worth £29k in your pocket before taking into account all the usual expenses associated with working. It might allow you to maintain your lifestyle but it could be a severe comedown in terms of take-home pay for a full-time job, probably with less paid leave than you've been used to. This is why you shouldn't yield to employers who try to palm you off with less because "you're already on a pension".