Is that just your Age60 pension benefits?
The commutation rate for converting pension to lump sum is around 1:20, so reducing your pension by £1,500 would produce a lump sum of around £30,000. Which using the 20x multiple to work out pot value, equates to about 15%.
If you wanted the full 25% tax free cash, that would be around £47,000 and would reduce your pension by another £800 ish.
*All figures are approximate and don't include any DBCBS, a small amount of which can often be used to fund some of the tax free cash with Age60 benefits, meaning the pension wouldn't reduce by quite as much.