Hi Pauline,
sorry for the delay getting back to you.
I have parents John and Margaret Pickering, with a baptism for Mark on 24 Mar 1776 at St Andrew by the Wardrobe, Blackfriars. I found that on the IGI, and I've not yet checked the parish records.
There was also an elder brother Matthew Pickering baptised 11 Apr 1773.
I've found no other children and no marriage so far!

Best wishes
Kevin