You didn't mention what passport you're travelling on, but assuming a "British Citizen" passport it's 240 hours transit without visa. I've done similar itineraries dozens of times from Manchester (usually on KL or AF) over many years without a problem; TWOV is really nothing new or special and thousands of people use it every day. If you're worried, get there early, have your onward ticket printed out and use the correct terminology, ie "240 hours transit without visa" (and not "transit visa" or "visa on arrival" etc).

I wouldn't think there's anything to be gained from going to Aether. In fact, if you are unlucky enough to come across a misinformed check-in agent, it may be easier to escalate it to a supervisor/manager from the main terminal.