My Peugeot 206, 51plate,speedo doesn't budge from 0?

I have been trying to fix my 51 plate peugeot for 3 weeks i have spoken to 4 mechanics who are all telling me different things...
1st mechanic said i needed a new speedo which would cost me 80 quid
2nd mechanic said that it was abs related then found out my abs was working fine
3rd mechanic said that it was my gearbox that had broken and i needed a new one which would cost 700 quid
the 4th one is sayin that its part of the clutch and can b brought seperatly!

Please can someone tell me what problem sounds likely! I have only had this car for 3 months and have had it serviced before the speedo went and was told everything was fine...