I don't know about guards, but contingency OBSs down at Southern, generally get 2-3 days of training for content including (but not limited to) announcements, emergency scenarios and procedures, customer service, minimumal operational requirements (checking for assisted travel at platforms and ramps) and some bare bones route knowledge.
without drawing the attention of the red pen, I’d be interested to know the reasoning behind bare bones route knowledge, when you’ve got situations of Hastings OBS working services to places like Southampton for the first time ever. Also, what are qualified OBS trained and expected to do other than passenger assistance, occasionally announcements and revenue duties?
do they receive periodic assessments and competency training?