If he is still enrolled at university then he may still be counted as being full time education and applying for PIP is not the same as having an award of PIP.
As this is not an area that we deal with on the forum I would get face to face advice to avoid his ESA claim being rejected due to his university course and there being an recoverable over payment.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems
