all of a sudden i am having difficulty getting gears and have to use a lot of force. its as if the clutch is not disengaging properly. the gearbox and clutch were replaced 33000 miles ago.
i think its a cable clutch but not 100% sure. is there any way of adjusting the clutch?
any help greatly appreciated

Is the clutch pedal sinking below the other pedals? If so:

Clutch Slave Cylinder;

Take the battery off,
Take the battery holder tray off,
Have a look on top of the gearbox there should be a piston type thing which is the clutch slave cylinder. If there is oil around this then its probably leaking and needs to be replaced.

Easy to do and doesent cost much for a new one from partco mate.