Place my clutch down and it wouldn't come back up took it to garage said needs a new clutch so fitted new clutch plate and bearing was fine for a few hours but started doing the same any ideas spoke to the mechanic now saying might need a master cylinder

The exact thing happened to my work van when I was going to overtake a bus that was stopped at a bus stop, went down to 3rd and wouldn't come back up. It would if I pulled it up but not on its own. Turned out to be the master cylinder.

Check the feed pipe to slave cylinder where it plugs in it as they have a tendency to fracture and leak fluid

How much should I expect to pay for master cylinder mechanic said is a main dealer part also roughly how long will it take to do

Id say either master cylinder or slave cylinder. Can you see any leaking fluid under the car?