....If that £25k isn't an immaterial amount compared to his pension then the technical term for his situation is 'stuffed' unless he makes some drastic changes.
.....
It's an interesting exercise thinking what could be done if a person woke up 6 years from retirement and realised they were in serious trouble.
First thing - absolutely stop spending money on anything but the barest essentials. No holidays, eating out, new cars, clothes, hobbies etc.
Then I don't think you could practically do better than pump the maximum £40k pa into a SIPP (actually £32k pre-relief) to get the 20% tax relief. That would give £240K invested after 6 years that could support £8k-ish pa draw. Anything left should go into ISAs then cash savings if there is anything left after the £20k isa allowance.
I think a house downsize into something cheap to run and maintain would be essential to keep the ongoing costs down, but that can wait a bit as it won't make that much difference in the 6 years.
That would give SP plus £8k-ish, say £16.5k pa. That would be do-able if you lived cheaply - small car, minimal holidays/travel, occasional pub meals out. It's a bit over minimum wage, but with a paid-off house that is doable.
On the less rosy side age 60+building&construction+brexit = high redundancy risk. It's going to be squeaky trousers time trying to make it through to 66 in full employment.
Fingers crossed the occupational pension comes good!