Sticking money in SSAS/SIPP - ouch on the way out?

Pensions are tax deductible so sticking money in (esp if it gets you below higher rate tax) is a no brainer, right??? Essentially saves about 21% corp tax on pension contribs (on a £100k turnover company) for the self employed PB company director who has a SSAS/SIPP?

On the way out said PB director gets 25% tax free lump sum and then the £12,500 personal allowance before 20% tax is due on your pension drawings. Higher rate 40% tax on drawings after about 50k.

So the real gain is that a quarter of pot is tax free via lump sum and corp tax saved on the way in.

So if the pot is worth 400k you will save about 20% of the avoided previous corp tax in taking a 100k lump sum (so are £20k up), but the remaining 300k will lose £60k in being drawn if you have used up your personal allowance before drawing?

Higher rate tax rates completely screw this 'deal'...

Have i got this right as sticking stuff in my SASS now looks less attractive... But it is good for IHT...

Thanks - brain spinning!

Thanks Rufus. Of course. I need a spread sheet to work this all out don't I! On the case! I think the IHT protection valuable too.