This will hinge on whether you are obliged to take the lump sum now, or if you can defer it, or, more likely, transfer it into another (possibly existing) pension fund.
If you are obliged to take the cash now, Payplan will want it.
If you are able to defer it or transfer it to another plan, then it would be possible to bargain with it, as this is money Payplan wouldn't get otherwise .... along the lines of, "If you agree to split the lump sum 50/50 to allow the purchase of a reliable vehicle to protect our income, then I will apply for the cash to be released. If you would not agree to the split then the money will remain vested in my pension fund and will not be available to either of us."
I would see if an expert comes along and comments on that tack, as it might be a non-starter

My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014