We were charged £16.99 for a three day stay and got an email to say we'd had a free upgrade to the multi storey. The directions for finding is entrance are not at all straightforward and it looked like we were heading to the paid drop off. This is quite a stressful situation. Anyway, we got there eventually after reversing back out and got parked. On collecting the car and putting the ticket in the barrier the machine said we'd to pay £150.00 for our stay. Not great, quite alarming, made us think we had got things totally wrong and had a hefty bill to pay. However, we called for assistance and the call handler put it right for us. So, clearer signage needed to the multistorey and tech solution needed to the charging system when you give a free upgrade.