Thanks for the input.
I forgot to mention I?ve already manually operated the the float as you mentioned. No leaks at all, works as it should. It?s just not happening at the correct level of stroke, can?t get my head around it, I?ve spent hours doing everything I can think of. I?ll give the bearing tap a go when i next take it off. Failing that I may have to increase the float height even more. I did look at taking the brass seat assembly out but it looks like it will be a destructive job. I may just have to live with it. It?s not a massive problem, like I say bike runs like a dream