What you can do is make use of the tax relief available, in a very cunning way. The Government blocked recycling of tax free cash over 10 years ago, meaning if you get a lump sum from one pension, there are restrictions on how much you can then put back into a new pension. If you try and put in more than 30% of your lump sum, or increase your current contributions by more than 30%, then they hit you with penalties.
However, if your lump sum is less than £7,500 then it's allowed. If it's more than that, you have to wait at least 12 months before putting it back into a pension. So for example if you're going to get say £20,000 tax free cash from the Teachers' Pension at age 60, if you take the cash and put it into say a 1 year interest account, then at age 61, pay £20,000 into a personal pension, then basic rate tax relief will be added on by the provider, meaning £25,000 will be invested. If you're a higher rate taxpayer, then you can apply for the balance 20% tax relief.
Bear in mind, as stated above, you're restricted to putting in a maximum of the lower of your taxable income or £40,000 in the tax year. If you run your own limited company then there can be scope for making up unused amounts from the previous 3 years, if you already have a dormant personal pension set up in the past.
Even a non taxpayer can take advantage of this, as non-earners are allowed to pay in £2,800 pa into a pension, and get 20% tax relief, so £3,600 is invested. Some companies, like Standard Life, even have a specific contract just for this lower amount, to be paid in, and instantly stripped out again.
In your scenario, provided the money has gone into a modern style contract which offers flexible drawdown, what you can do immediately after investing the £25,000 gross, is take out the 25% tax free cash allowance from that pension (£6,250), and leaving the rest untouched. As that sum is less than recycling limit, you can put it back into a pension, and get tax relief on it. Again. So £6,250 becomes £7,812.50 invested for a basic rate taxpayer.
Rinse & repeat.
Obviously these higher amounts are only possible if you have the taxable income to justify the contributions in the first place. And you still have the other pension funds invested, and being in a pension, they don't form part of your estate if you were to die, and can be passed onto any named beneficiary.