Found it Mick
When this lousy war is over

Not all trench writers were famous. Not all were polite. So some very well known hymns took on very colourful lyrics. One was Joseph Scriven's What a friend we have in Jesus. From the trenches came When this lousy war is over:

When this lousy war is over no more soldiering for me,
When I get my civvy clothes on, oh how happy I shall be.
No more church parades on Sunday, no more begging for a pass.
You can tell the sergeant-major to stick his passes up his arse.

(Repeat first two lines of first verse)
No more NCOs to curse me, no more rotten army stew.
You can tell the old cook-sergeant, to stick his stew right up his flue.

(Repeat first two lines of first verse)
No more sergeants bawling, 'Pick it up' and 'Put it down'
If I meet the ugly bastard I'll kick his arse all over town