Peugeot 207 gearbox selection stiff in cold weather

I am the owner of a 2007 207 1.6vti. At low temperatures, selection of gears feel like you are trying to push the gear stick through setting concrete. After 10-15mins of driving the selection frees off and feel much better.
I have changed the gearbox oil (which made no difference to the symptoms) and also disconnected the selector cables at the linkage to ensure there was no binding. They are free and smooth in operation.
Has anybody come across this before? or is familiar with the gearbox fitted to the engine?
Any ideas?

 

hi...I own a 1600 I Peugeot 308 2011....second gear is a bit knobbly...grabs going into second gear...how do I adjust clutch cable to to stop this happening....thank you.