You are correct about the 25% tax-free.
However, you can then leave the other 75% invested and "draw-down" what you need each year.
So, for example, you could take out £10K a year and it will all be tax-free (providing you don't have any other income or state pension).
The theory is that you can take what you need to top up your state pension and whilst leaving it invested, it will last a lot longer than handing over all your money and buying an annual pension.
FWIW, I agree with you paying your debts first.
My view is that people have had it drummed into them to save, save, save for your pension without considering that you will need way less money in retirement than you do now (whilst paying a mortgage, paying for family holidays etc.) This is why I prefer the balanced approach of putting a small amount in your pension whilst making sure you do the big things now (whilst you are fit, able and have all your marbles!)