If I put it into 6th and apply no acceleration it doesn't high rev, it goes into gear but as soon as you try to keep the speed up and apply power it revs out like the video.
I had a genuine clutch put it when the gearbox was out. It doesn't seem to be the clutch since it done this on the old clutch too (which was fine when they took it out). All other gears work fine with no issues.
Not sure where to go from here, might just have to trade it in and take the hit.