hi david,
you have started searching here,
for ww1 he would have been to young unless he signed up underage only one david pickering in the Manchester regiment in ww1,and 9 in other regiments
i think it would be a good idea if you posted the photo then others could help you out with the time period
ww2 records
,http://www.mod.uk/DefenceInternet/ContactUs/ServiceRecordsEnquiries.htm
Medal card of Pickering, David
Corps Regiment No Rank
Manchester Regiment 58416 Private
Border Regiment 31402 Private
Date 1914-1920
Catalogue reference WO 372/15l good luck tonyrod