As it says in that Sky News article, what really needs to happen is to prevent people who aren't eligible from booking in the first place. Once they have booked - potentially taking the slot from someone who is higher priority, it seems fairly pointless turning them away, as that slot can't then be used by someone who is higher priority - the ship has sailed.
When I went for mine, two people (one on front of me, and the one behind) were both sent away as they weren't actually health care workers. They had obtained the link to book from elsewhere. However, they had obviously lied during the booking procedure, since we were required to provide a lot of detail about where we worked during that. This was followed up with ID checks at the door - hence people being turned away. I think the system in other areas is different though - if no questions are asked during the booking and you don't have to lie in order to book a slot, then that really is a failing of the booking system. It's hard to blame people for doing it.
The problem is also that preventing ineligible people from booking whilst also allowing the system to run quickly is difficult. There is no central database of "front line heath care workers" and it is not something that is attached to NHS numbers for quick identification. Preventing those who are not in the age related priority groups should be easier, as this can be identified from NHS number alone. But the system cannot simply run on age, because the criteria do not run on age alone. I'm sure a more secure and robust system would be possible, but it would waste precious time setting it up.
I tend to agree that getting the vaccine in to as many people as possible is the aim, but I suppose there needs to be collective social responsibility to avoid too much of the elbows-out, survival-of-the-fittest that inevitably occurs when large groups of people all want the same thing.