Try eating your evening meal earlier in the evening so that you know your bolus dose is exhausted before bed, after this time try testing your bg every 2-3 hours during the night, in theory if your basal dose is right it shouldn't fluctuate much by -/+ 1.5mmol, if it does then you need to adjust your lantus accordingly.
I eat my evening meal around 6-7pm, thereafter I don't eat till I wake at 6am, provided you eat enough calories in your main meal you shouldn't need to eat again before bed.