I have experienced similar symptoms, and had been thinking maybe a clutch was in need. From what I could tell the problems were in 2 parts. 1 - the clutch pedal is incredibly stiff and the biting point is a little on the low side.
2 - Putting the car into either 1st when moving off, or 4th when coming down from 5th had become very awkward. Going up into 4th from 3rd wasn't great but easier (I suspect due to the moving from planes moving from 5th to 4th).
In the case of 1 I'm intending to fit a new clutch cable, then adjust it to the right level, etc.
In the case of 2 I have just changed the Gearbox Oil, and I reckon it is most likely the solution to your problem. I used 75W80 Synthetic Oil (2.7L are needed)- Castrol SMX-S available at pretty much all Halfords, and shifts are now much better. 1st goes in every time no problem, and 4th is almost spot on. Wierdly the car feels a bit quicker. It might always be me, and most likely is but I'm much happier. You'll need a 17mm Allen Key to drain and refill the sump. Halfords also sell these as a 3/8 inch socket so if you have a socket set you're half way there.
(First you'll want a container to collect the oil, then you'll need to remove the sump cover on the base of the car to get access, then the drain bolt is on the base of the Gearbox, which you'll drain into the container. After that you do up the drain bolt (25 lb ft / 18 nm according to Haynes Manual), and you take out the filling bolt which is on the side of the gearbox, and fill it by squeezing the new Gearbox oil into it. We found that the last 100mls of each bottle was a pain in the neck to go in, so since you need 2.7L we used 900ml from each bottle, and then put the remain into 1 bottle for the possibility of topping up - which ain't going to happen

, then do up the bolt (same torque rating), and you're finished - I was surprised by the small bits of swarf (metal) that came out with the oil which will have been swirling around doing lovely things :S but then my brother pointed out a friends munched up gearbox let out half cogs, etc Must have been fun

).