He was William Gridley, regimental no. 1720 and would have enlisted in the 10th Hussars around early 1854. From this he would have been 18, so gives a birth date of approx.1836. try all the census's from 1861-1901 and see what you get. There might be a lead there.
Roy Mills Editor "The Lives of the Light Brigade" www.chargeofthelightbrigade.com