A regas may sort it but much more than likely your compressor has failed, the most common cause on these cars. When I bought my car cheap, with the econ light on, nearly eight years ago a simple regas sorted it for about 4/5 years though the well known pulley rattle was present (caused by perished rubber in the pulley). Since a new aftermarket compressor (around 250 quid) all has been fine. It is very important to renew the dryer, at the same time, which are around £15.