So let me get this right. For £5 per person each way you get a transfer to Calis Beach. However (and not surprisingly nor am I having a 'go')you might have to wait 'up to' one hour until other travellers arrive at the airport.
Sounds like a fair deal to me - even with the hour wait. Only problem I can see is if they have 5 couples on one transfer that someone is going to be last off. This, along with the possible hour wait, could add considerably to your transfer time.
Keeps the cost down though.