gear change very hard

hi everyone.
My discovery 2 td5 manual is having problems changing gear.
It went from been good to bad in no time at all. All gears are really hard to get into except for 5th.
I've changed the oil with mtf94 but it has made no difference. I've checked clutch fluid and its full to top. My clutch has always had to go right to the floor to change gear. Been like this for the 2 years I've owned it. Is there anyone with any idea what it could be. Due to do a 600 mile round trip in a couple of days and not sure it will survive this way. All gears are really stiff and notchy but 4th and 1st completely block sometimes although it goes in to 4th a bit easier if I dip clutch and shoot the revs up a bit as I change gear. Any advice much appreciated.

It could be the plastic bush that locates the ball at the end of the gearstick in the selector rail. It's a relatively common failure on high mileage cars.
When it gets worse you can might not be able to select any gears,
The possible alternative is the gear selector plate being worn / loose. However, from my experience, you can still always select a gear - even if it's difficult or requires careful positioning of the lever.
If it's the bottom plastic bush, it's a possible cheap DIY fix, but it will take a few hours as you have to remove the centre console & transmission tunnel cover plate (lots of pop rivets to drill out).