Does 28th Dec bank holiday relate only to office workers.?
If you would normally work on a Saturday but the shop is closing then you are having your Boxing Day Bank Holiday. Monday 28th as a Bank Holiday is for those people who do not normally work on a Saturday and would therefore lose out on the Bank Holiday. Christmas Eve is never a Bank Holiday so if your shop is closed that day and you would normally work it then the employer is perfectly entitled to ask you to take a holiday for the day. So, in this case – yes you do have to use 2 days holiday.