The two sat down in the second photo are from the Irish Guards. My dad seems to think that my Grandad spent some time in an Irish regiment such as the Irish Guards or one of the Inniskilling's (Dragoons possibly).
He also may have spent some time in the KSLI.
He was from Shrewsbury, Shropshire.
But I do agree the badge in the second phot does look like an Artillery badge.
Thank you all for your help, any more ideas are welcome.
One other way I'm trying to track his movements is from the location of a Field Post Office (867) any ideas where I can track this down?