I had a new condenser fitted a couple of years ago to a qashqai. I think it cost over £700 + .It was a hard pill to swallow but it was a baking hot and I had to go on holiday with the car.
Having looked into it a bit later it looks like a job I could have tackled myself given the time .
there is a video on youtube of it being done. I think the actual fitting could be done yourself and then you could have the system re gassed by a garage .I don't think it answers your heating problem tho