PB, you can use up what's left, but that's the last time you're using that flour.
Foul tasting vital wheat gluten AND it only clocks in at a paltry 11%? They've got a lot of nerve selling that stuff.
In Ireland, you have one advantage that we don't, our nutritional labels work with small quantities and round the numbers, so they're useless for gauging protein levels. With your 100g serving label, you can gauge the protein far better.
Start looking, in multiple markets, for any flour that references 'strong' or 'Canadian' or both. Your goal should be either 12, 13 or 14g of protein per 100g. The ingredients should NOT list vital wheat gluten.