Michael and Jeff -
I should not have butted into the thread in the first place - having just joined the Message Board that day, a month after Michael's original post. My apologies if I misled you Michael.
Generally the safest methodology would be to use the tried and true "work backwards from what you know". There seem to be only four James Fox who were discharged to pension from the British Army who were born in Ireland 1837 (+/- 2 yrs). Thus if you get back to an Army career and Fox received an Army pension, the odds are reduced considerably.
I hope you find your man.