If you don’t currently have the original photographs in your possession I would recommend contacting the owner and asking for back views of the card mounts: seeing the location (if provided) and any annotations might be key to solving this conundrum
Do be aware that medal cards and the corresponding medal rolls, only provide regimental details from the date the soldier embarked overseas. This is because their sole purpose is to confirm medal eligibility, thus any previous units served in whilst stationed in Britain are never listed