Hi sas401
The first thing I would say is legacy ESA does not exist for new claimants, new claimants can now only apply for New Style ESA, why DWP called it New Style ESA only they know, the only reason I can find is to confuse claimants and advisers.
DWP are correct, what ever amount you receive by claiming NS ESA will be deducted from your UC claim. One of the advantages I can see is, NS ESA is paid quarterly and class one NI contributions.
With UC you can claim if eligible, LCWRA which will give you an additional element worth £390.06 pm
I'm afraid a relative cannot purchase the NI Contributions or Credits that you require, you can only purchase Class 3 or 4 NI Credits and you need Class 1 or Class 2 Contributions and/or Credits which can only be acquired through paid employment or registered self-employment.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
