It would be helpful to list what tv does
but my memory is that this is 720 plasma with 2 HDMI?
and freeview, it came out in 2006 which makes this a good 4 years old.
It probably cost a bomb when you bought it but you could buy a brand new similar specced TV with warranty and more features but still a 720 HD Ready but probably better picture motion handling etc for 400 pounds and change.
In my world I would never pay more than 50% for a 4-5 year old TV, so 100-150 is about all its worth. Unless 200 pounds was a life's savings to a person I cant see why you would pay more than 200 pounds for such a TV.
It would make a terrific second TV for bedroom or study, gaming machine.
To put it in perspective (and maybe this is what you have noticed), one of the highest rated 50 inch TVs 1080s (LG 50PK350) is currently being sold for less than 600 and is quite a bit better than your old panny.