My role is one where there is potential for and high likelihood of progression up the pay bands over the next 10 years or so. My partner thinks this will compensate for the 18 months or so of lost pension, since I'll be paying in more to my pension when I climb up the bands and opt back in. He thinks it will even itself out. I'm not sure if this correct... I'm just trying to do what I need to to keep us afloat for now.
So:
a) You're not married, and therefore entitled to none of your partner's still-growing pension if you were to split
b) You're not sure this is the best course of action but...
c) You're considering it (or have already done it??) because HE thinks it's the correct thing to do?
No, no and thrice no. Your NHS pension is probably worth more than his (as you're the higher earner - on top of the NHS pension scheme being gold plated) and as PPs have said you would lose out doubly because firstly if you're not paying into the pension scheme you lose tax relief (and you must pay more tax then him) and secondly the amount your NHS pension is topped up is massive compared to other schemes. So overall stopping paying into your pension may not save you as much as you think (in both the short and long term).
On top of all that he is merrily continuing paying shed loads into his own pension (are his overtime payments pensionable?), which you would have no claim on in a split. All this is doing is worsening your financial situation, both jointly if you stay together and yours alone if you don't.
If you've been managing the debt repayments so far then keep on as you were, continuing to pay into your pension.
If you can't do that then find other ways of cutting back apart from pension payments - kids won't notice 18 months of no holidays/cheap days out/small presents. You should be able to manage without lots of things for only 18 months (it's unlikely you'll all need new winter coats within that time frame, for example).
If you can't do that then keep your pension payments up and stop his.