More more more, I’ve located more sites to search when it comes to ancestors being involved in wars.
By now we should have it penned in that searching the National Archives is a very good starting point, so in this case have a search through http://www.nationalarchives.gov.uk/documentsonline although I just checked this site to make sure it was still up to date and found that the site to check now is here.
For Royal Marines, a good way to go is through http://www.findmypast.co.uk
If you have a name you want to search then you can do it for free at http://www.cwgc.org
For burial locations and more information on them, take a look through http://www.1cemeteries.com
There is even a war graves project happening at http://twgpp.org
No idea what ranks are what? A look through http://www.en.wikipedia.org/wiki/British_Army_officer_rank_insignia should help