This is incorrect. You can continue to invest the 75% that remains undrawn in your crystallised pot - usually in identical funds/stocks/shares that they were invested in before they were crystallised. The crystallised funds do not have to sit there in cash.
It might be that your chosen provider does not support it, but most SIPP providers do.
Interesting, thanks for the correction, that must indeed be a 'feature' with my current provider. In which case I think my preferred approach would be to take my chosen level of tax free cash to supplement my regular income, plus £20k/£40k to fill up one or two ISAs (depending on being married and trusting your spouse with your money
), then at least all the subsequent growth will be locked in as tax free. Otherwise if it grew inside your pension you might exceed the tax free cash amount over time and end up paying more tax than necessary.
Admittedly that's a very nice problem to have!
If you trust your spouse....
There is nothing to stop you withdrawing money from your pension pot, and paying it into a pension pot for her/him. The govt will then top up your payment with tax relief at 20%. So for every £100 you pay in, her/his pot will grow to £125. There are some limits, but IIRC you can pay in at least £10K p/a to your spouses pension pot.
Then when she/he retires, she/he will be able to take 25% of their pot tax free, and the remaining 75% at their marginal rate. Depending on their state pension entitlement, some or all of this could be within their personal allowance, so could be 0% taxed.
This is all the sort of stuff that a good IFA will sort out for you. And no, I'm not an IFA.
If you don't trust your spouse then you're probably already oppsed.