Yes, I can see that. 65" wouldn't physically fit. This is about aesthetics and available space. There's only one spot to put the TV which a 42" fills well. A 48" would be 3cm wider on each side. That works. The height though would be 11cm greater. That doesn't work in our little cottage. Squirrel Nutkin book is the extra 11cm height.
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I see the problem.
I bought 65" for the main lounge which is over 18' long. Now I am in the flat it was touch and go but with a bit of faff we got it to fit.