Back again!
I myself ended up biting the bullet and getting a 'specialist' out to diagnose my problem.
They told me it was the defrost stat, but that came as part of the evaporator/heater assembly, which I would need to buy. In addition due to the excessive ice build up in the polystyrene air ducts and fan assembly, that would also need replacing.
I agreed to this thinking it would solve the problem - costing around £240! But I thought at least we'll have it working again!
Within a couple of weeks of the parts being fitted it was showing signs of the original issues (clear solid ice 'flowing' out of the air ducts in the freezer compartment.
I called the company back, they tested everything and said all was OK - they tried to blame freezer being full and other things!
I ended up claiming through CC company and did get reimbursed the cost of the repairs - the problem was still there!
The strange thing is, the defrost heater is working as I get water accumulation around the compressor tray.
It appears to me as if the heater and the compressor are running at the same time? The ice is melted by the defrost heater, but the running compressor immediately freezes the water (hence it being clear?)
I've lived with it for a while, but it looks as though its getting to the point where the circulation fan will start sticking stopping the airflow, i can hear it catching when running occasionally!
Did anyone with similar issues get a definitive reason for the issues and a working solution?
Thanks
MIB