Understood - it sounds like you've already looked into PILON in some detail then. I gather that if an employment contract includes clauses suggesting that PILON is an option (i.e. planned for) then the tax office tend to treat any payment as taxable income, and similarly if the company has a 'history' of doing it as a matter of course. I'm not sure who the risk lies with though - if the company gives you a lump sum outside of PAYE, and the tax office subsequently decides it should have been taxable income, is it the company or individual who would then pay the tax? If it does take the tax-free route I'd suggest you make sure that it's in the agreement that the company takes any such risk. If you haven't already, it sounds like advice from CAB or ACAS (etc.) is in order (they can probably advise on the legality of the redundancy consultation process too).
Further apologies if this is drifting too far OT/obvious/etc.