Thanks for the replies guys. It's not because it needs running in, got 12000 miles on it and not an issue changing down the gears, just up, so blipping won't help. Having had a look at the mechanism it does all seem a bit loose. I'm not very mechanical and don't know the correct terms but even the grooved shaft that the linkage is connected to that enters the side of the gearbox has some play in it, it can be moved in and out a little, not sure if that's a bad sign but can't see anywhere external that it could be tightened up.
It's definitely a two stage gear change, trouble is sometimes the second part where the gear is actually engaged doesn't seem to want to happen, takes a pause and an extra kick up