Attached is a summary of his service. You will see he spent most of his service in Macedonia on what is also called the Salonika campaign. There are unit diaries covering most of his time but only the Sep/Oct 1915 period in France has been digitised. If you wish you can download that from the National Archives at
http://discovery.nationalarchives.gov.uk/details/r/C7353410 although there are only 8 pages of detail and their activities were confined to building and mending things. The diaries covering the company in Salonika would cost to have copied.
That said, the RE Museum Archive has a summary of 108 Field Company covering Dec 1914 to Sep 1917 and a diary for the Mining Company in Salonika Jul 1918-Jan 1919. I would suggest getting in touch with them
http://www.re-museum.co.uk/ to see how you might go about getting these.
The diaries won't cover his whole service.
You'll need to do some Googling and reading to find out more about the Salonika campaign, it has been called the forgotten campaign as the spotlight falls on the Western Front most of the time.
MaxD