PrettyLittleThing Premier Delivery Rarely Arrives Next Day and Feels Misleading

I registered for the Premier Delivery program of PrettyLittleThing, which apparently covers "next day delivery" on every order. It has, nevertheless, been a major disappointment. I have used it several times, however my orders hardly ever show the next day as stated. I recently ordered some clothing on a Sunday for a Tuesday special event, but I am now informed they won't show until Thursday. I feel completely mislead since the things are being sent by Royal Mail's Tracked 48 service, not even next-day delivery. Customer service dismissed me when I contacted them, claiming delays were normal. I feel like I squandered my money on a useless service and am quite let down. Pretty Little Thing should at least provide Premier service reimbursements should they break their pledges.