It's a *9-hour* flight. How tall are you? 'Do the Math', as they say!
If its Thomsonfly leg room isn't too bad Thomas Cook forget it. I would still say though if you can afford it go for it! we did flying out last year on Thomas Cook but the option wasn't available coming back it was bad but we were only on a 4 hour fligh.
I have flown to the Barbados non stop to do a cruise but I am only 5ft.4" so if you are tall maybe a good isea to upgrade - if you can afford it - do it anyway!!!! - enjo.
We flew with Thomas Cook and there was no legroom at all. Im 5'9 and i couldnt put my knees straight!! Eating was also a nightmare as you are so crammed in. It has put me off flying with Thomas Cook again. Go for the upgrade definelty.