The other day I watched Johnny English 3 - I paid for a regular seat, but went up to Premier.
If you sit one away from a line of people, that seat almost certainly won't get booked as the system doesn't allow "orphan seats" to be left, and people generally want to sit away from groups. If someone books that seat in the meantime, just pretend to look at your ticket, say OOPS! and move one along
