According to FreeBMD, the only people named Hubert Foreman who were born in the relevant period (i.e. when they could have later served in WW1) were these:
Hubert Charles Foreman (b. Blean, Kent, Dec 1874)
Hubert Foreman (b. Faversham, Kent, Jun 1886)
Hubert Leslie Foreman (b. Blean, Kent, Sep 1894)
Assuming that the middle initial ('H') to be correct (and equally assuming that his middle name might have been omitted from his birth certificate) the most likely match would seem to be the Faversham one. FreeBMD further suggests that he married (also in Faversham) in Jun 1907.
http://www.freebmd.org.uk
Using those starting points, you could research further using paid subscription services (such as
http://www.ancestry.co.uk/ , which offers a free 14-day trial) or order copies of his birth and marriage certificates from here:
https://www.gov.uk/order-copy-birth-death-marriage-certificate