Hi, I took a look at the Alderney records held at the Priaulx Library in Guernsey, but sadly there is a gap between 13th May 1871 and 13th Dec 1874 where no records seem to have survived. A check in Guernsey's Civil Register index also drew a blank for the surname Gurney in that period.
I'm sorry I couldn't do any better.
Andy S.