Right, here's what you need to do.
Go the the General Register Office site:
http://www.gro.gov.uk/gro/content/certificates/
You will need the following info:
Lawrence Fletcher Mossom
Born 1901 (Jan, Feb, Mar)
Barton Upon Irwell, Lancs
Volume 8c
Page 684
This will cost you £7. They will send you a copy of his birth certificate.
His father's name will be on this if his parents were married. If they weren't, his mother's name will be on it.
If you want his marriage certificate as well the details you need are:
Lawrence F Mossom
Married 1928 (Oct, Nov, Dec)
Manchester South, Lancs
Volume 8d
Page 151
That'll be £7 as well.
Once you have his father's name you may well be able to track down more family members on the census records.
Good luck!