Replacement gearboxes for 55 plate

Hi all,

Had problems last year before crimbo with the car not easily going into gear when weather and engine were cold.

After some investigation I had the slave cylinder changed (along with clutch and flywheel as it made sense).

Turns out the slave cylinder was leaking and not getting full travel.

Ran it over xmas and it was loads better but gearbox still felt out of the norm, so we changed the fluids.

Turns out the previous own had had the wrong oil put into the box and when drained lots of metal teeth and shards came out with it.

Now its running fresh thin skoda spec oil its worse than ever, crunches almost every change between 1st and 2nd, and third in cold weather.

Obviously replacement box is the best solution until I can find the time to repair the original box if its worth it.

My question now is: I heard that there was a difference in 6th gear ratios around the late 05 to 06 years and I can't find the differences between codes using the search???

Does anyone know if there's any difference at all?

Car is:

55 plate VRS with BLT engine.

Cheers all.