I tend to agree ..the 10 mana should be good for a over 90 kg guy ...FIRST BOARD.
i have a mate that is 85 kg and he loves his 10'mana ..because it is a good size board.and he has no problem riding it in all conditions ....and he does flat water paddling .
If you are a real good surfer and what just a wave board as bris kites say ..maybe the 9'5..
because its ya first and learning the ropes is in mind the 10' is the best ..I learnt so much on my GT 10' mana .
it wasn't till I start surfing the big waves that I needed a smaller one ....
GTW beauty .
being in the UK you won't fall off as much on a bigger board ..and the water is quite cool there ..