The first thing you need to decide is between LCD or OLED. There are pros and cons to each, so make sure you read up on the differences, both on here and elsewhere.
If you want a high-end 65" set then the best choice is OLED with your budget, IMO. As you've probably found already, you can get 65" OLEDs from all of the major manufacturers within your budget.
I don't buy into this 'LCD in a bright room / OLED in a dark room' argument at all... at least provided the TV isn't going in a conservatory ! OLED screens can be fairly reflective though admittedly, so it's worth taking the position of the TV in relation to any windows (and the time of day you do most of your viewing) into account when making your choice but, FWIW, I have no major issues viewing my OLED in a bright room.
Also - while the risk of 'burn in' on an OLED is probably fairly low (with normal use) these days, an OLED probably isn't the best choice if your TV is likely to get paused for extended periods of time or you spend many hours a day watching news channels or breakfast TV.
Whatever you go with, my advice would be to buy from a retailer that includes a free extended warranty in case of any issues. My choice was Richer Sounds, but John Lewis, Costco and AV specialists such as Sevenoaks or Crampton and Moore are other, popular options.
Here is some useful reading to get you started on some TV choices...
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