Thanks everyone for the help and advice. I took it to a specialist Air con garage that was recommended to me and I am so glad that I did. The fault was showing on the cars computer as a faulty sensor. This from Lexus would of cost £100 to diagnose, £300+ for the part and god knows what to fit and then regas.
The car was diagnosed, part charged and the car fully regassed for £110!!!
Outstanding service, knowledge and value. If anyone ever has any AC issues and lives in Kent borders with London I fully recommed;
Mark from AirCon Direct in Northfleet in Kent. Superb