Don't know if you have kwikfit in your area but they will connect the Aircon to a machine that removes the old refrigerant and lubricants, does a vacuum test for leaks and refills the refrigerant and lubricant. If is still doesn't work they don't charge you. If you are sure it's this specific valve, where is that? Is it on the compressor pump?
I got a brand new aircon pump for the VRS for £156 off eBay, fitted it myself and kwikfit recharged the system for £50. Aircon is running great.
I would find out more about this valve. See if you can get a reasonably priced replacement and check out if you can fit it yourself or get an indy specialist or Aircon company to do it.