Our Anglesey is a 5 man tent, usually there's only 2 of us and when the kids join us there's 4. I love the huge living space too, it's cosy even when it's raining outside and you don't feel claustrophobic.
There`s four of us, and we have a 12-man tent for long trips, and a "small" seven man one for weekends.
Buy whatever size you like, that`s my advice. But....if you`re going for a mega-large tent, then think about whether you`d be prepared to occasionally pay extra for a larger or double pitch for it, and where you`re going to dry it out when you bring it home soaking wet.
we have the Vango aspen 500DLX for 3 of us , its a great tent load of head room all round , including in the sleeping pods unlike some of the tent, down side is it comes in 2 bags, one for the tent and one for the poles which is heavy ! , its relatively easy to pitch , but once its up its great light and airy, my advice would be to go to a camping store and look around the display and see what you like and can afford.
we have a diablo 900 for 4 of us lovely tent lots of room and our weekend tent is a coleman canyon 8 only use 1 sleep pod and there enough living space for weekends,only down side to coleman tent no sig.
It's always best to go with the largest one you can afford, although I would only recommend a frame tent if your going for a week or so. A big dome or tunnel tent is a good choice. Modern nylons are so light & strong.