only gear it does it in and only at speeds 40mph or above,serious issue or should i not worry to much yet

 

I had something similar, especially when the box had warmed up a bit. It would crunch but if you got the gear change just so would go in fine.

I changed the oil for some nice fresh syntrax and hey presto it has gone away for now. I am under no illusion however that something may let go in the future. Got to be worth trying some fresh oil before you do anything?

 

sounds like worn syncromesh baulk ring mate, oil may help but i fear the damage is already done.