As already mentioned would have to be the 55" Samsung TU8000 can grab this for £549 now.
Otherwise if you hate Samsung's, then you can nab a Sony Bravia KD55XH8096BU for £649 now, but means adjusting your budget a bit more.
The Hisense U7QFTUK might be worth considering, it has full array local dimming and a decent peak brightness for its price range so it performs adequately with HDR content. You usually need to spend a fair bit more to get a TV that's actually competent with HDR from what I've seen.
https://www.avforums.com/reviews/hisense-u7-4k-lcd-led-tv-review.17094
It's currently £519 from Richer Sounds with the RSTV30 code for the 55 inch model:
https://www.richersounds.com/hisense-55u7qftuk.html
Thanks both for the replies, the Samsung looks pretty solid. I am in the middle of buying the house so I will likely have to wait till im in really before I can buy it. Both Samsung and Hisense look to have everything I need, not really sure if there is any difference (or anything I would notice anyway) as I said its going to be a living room workhorse really.
I think I would prefer Richersounds because of the great warranty they offer, if I stretched my budget how about the...LG 55NANO866NA
That really would be my max though. Or is there no real difference between the LG, Samsung and Hisense?