A Hasseblad for 50 quid sounds like a door stop Kev.
Add in the fact that it's jammed and has a cracked mirror and it doesn't sound at all promising to me. I reckon if you're a really handy type and can tackle the job yourself, it might be worth a punt. Bear in mind though that at this price this sounds like a very old model you may well not be able to source parts for any more. You could end up scouring the web for donor cameras for the bits you need. Even if you could find a repairer who can do the job, I think the cost would be onerous. I was quoted around £150 to replace the seals in my RB67 body and one film back, but they wouldn't quote a firm price. In the end I did the job myself and sealed the body and 4 backs for the cost of a seals kit - just a few quid.
My gut instinct unless you're really after the challenge of fixing it is forget it - there's a huge choice of MF cameras out there at the moment.
It was just a bit of speculation that's all. I've got no problem pulling it to pieces (putting it together could be interesting ) and to be honest there's no way I could get into a Hasselblad system given the prices of the other items but I thought it might make a bit more when fixed and help me get the money together for a systems I could buy into. Out of interest it's a 2000FCW about 1984 I think.
Still too much for me at this point in time, I should really have more patience but it's never been a strong point of mine. That 500 reminds me a bit of Sony cameras. A reasonable price to get started but adding to your lens collection will be more expensive than any other manufacturer like for like.