2000 Ford KA unusual clunking sound

This car has seen better days. A new problem has arose and I could do with a diagnosis and an estimation of how much it would cost to fix.

I have been driving it for 3 months and when I got the car, I was told that the clutch had just been replaced. I have had trouble with gears grinding since the beginning (1 in every 3 journeys roughly) and I find that for me to go from 3rd to 2nd the clutch has to be in a certain position, also the same for the reverse gear otherwise it won't have it. More recently for the past week I have had difficulty with getting from 2nd to 3rd.

Today I was going round a roundabout, trying to get into 3rd, gear grinding, then I stop at the traffic lights. A repeated clunk now occurs every 5/6 seconds whether the clutch is depressed or not. Also when it is idle and in 2nd gear. I don't know about 3rd or higher as the sound and vibration of the engine masks it. But I can only feel the clunk through my foot being on the clutch pedal. It doesn't seem to get any faster when going quicker either.

Sorry to be so thorough with my description but no other forums seem to be matching my "symptoms". Hope someone can help and thanks for taking the time to read!