Op, please tell us if it is a defined benefit or defined contribution pension.
It sounds like you have a defined benefit pension (but could be wrong) and will be sacrificing yearly pension which is index linked (inflation proofed) for a lump sum, which you have no specific plan for.
Remember, inflation erodes the value of a lump sum sat in the bank. So that chunk declines in value, plus you have less per month, ossiblynfir 25-30 years to live on. Often the commutation amount is 1:12 meaning you give up £1 of pension for each £12 you take. It’s not a great rate given how long most live.
The time it can be worth taking the lump sum is particularly if there is a chunk of mortgage to pay off, so it can mean there are no housing costs to come out of pension. Or so sometimes people have a plan for retirement such as buying a camper van and travelling or doing a big building project or giving their child a big chunk of cash towards property. These specific plans for the lump sum mean it get spent before it’s eroded and achieves a particular goal. As long as it doesn’t reduce the regular pension payment so it’s hard to live, it can be very valid.
The last time when it might make sense is if a pension pays out before all pensions payout and you need to ‘bridge the gap’ for example to state pension when you will get another £9k if you qualify for full state pension. Sometimes people know they will be well off at 66/7 but the pension they get at 60 won’t be enough to live and they really want to stop work. The lump sum can be used to add to the pension already being achieved and split between the 6 or 7 years until the rest of the pensions payout, meaning stopping work at 60 is possible, rather than needing to work longer. This too is very valid.
Don’t take a lump sum just to have some savings for no specific purpose. And make sure you understand the nature of your pension and how it all works. Don’t cash in a defined benefit pension for a lump sum without getting some advice....you could lose out significantly.