For those who are inexperienced Cruisers, or even just thinking about their first one, there's a wealth of advice out there, on various forums. Cruise.co.uk is just one, you'll find very few questions that you can think of that haven't been asked and answered before?!
We've been on about a dozen cruises, assorted lines, not Cunard but we've met folk who were semi-regulars with them.
I'm afraid we got the impression that the line suits folk who are trying to "get one up on the Joneses" - also those who like a very trad way of doing things. And that's not for us, we swerve the fancy dressing-up nights wherever found, use the buffet instead (so then you can have 3 starters and 4 puddings if you like, or just a main course, whatever?!).
The 'Curly' mention that "Oceania was head & shoulders" was quite amusing, that line is one of a group that we call the '6 star' group, where service is off the charts (& and some lines are 'smart/casual' too) but as stated the prices reflect that! Other similar high-standard lines would be Regent, Crystal, Seabourn, Silversea, and perhaps Viking too.
A line called Azamara also offers an 'upper class' experience, also very high on the service scale, smaller ships though (which some prefer) and not quite as dear as the 6-star group!
An alternative to Cunard for Brits of the more mature age scale would be Fred Olsen, tried and trusted offerings (but likely an older ship).
We liked Celebrity as a line, but if you choose them you'll likely meet a higher percentage of American and European passengers, depending on the route. But remember that Chump was only elected by a minority of Americans?!
These days we are wary about flying (so much hanging about!) and that reduces your cruise options of course!
Lots of website bookers, we always had good service from 'IGLU' (I think they have a skiiing dept too?!), and I think Bolsover Cruise club (ties in with a recent 'Peak District' thread?!) are also OK.