I wish the cold water side in my gaff was routinely between 20 and 50! It would save me a fortune in heating bills.

as Graham said, if it's in L8 you should do it, but if you don't you have to prove in a court of law the you have followed the provisons of the code or have something better, remember legionella is now covered under corporate manslaughter so prepare you bed in a cell.

Copper/Silver Ionisation - can facts be checked before comments are made please?
I thought this blog might have some specialists input, given it will be read by the original author looking for facts.
This is exactly what is meant by the use of inappropriate or incorrect advice or comments being made when it comes to water hygiene. The FACTS ARE:
An EU Directive called the Biocidal Products Directive with the Biocide Products Regulations 2001 gave notice that, as from 1st February 2013, it became illegal to market, sell or use copper/silver ionisation systems that produce copper ions that are displaced into the water system for the control of Legionella. It is an EU-wide ruling applicable to the UK. If in doubt, please refer to the HSE website.
The HSE has, however, submitted an essential use derogation notice to the EU Commission requesting the UK be allowed the continued use of the systems, but the decision to allow their use will be made by the EU Commission after completion of a 60 days commenting period that ends on 20th April 2013. Whatever the EU Commissions decides will be final. If they decide the systems cannot be used in the UK, that will be the end of the such system in the country.

Unfortunately there are too many individuals and organisations offering erroneous legionella advice. Even advice correctly given is often misunderstood.
In this case, the description of water temperature requirements given to the customer is partially correct. To explain:
The Building Regs Part G, edition 3, has no reference to either 50degC or 60degC in connection with legionella prevention, although it makes reference to water being distributed from hot water generating plant at temperatures no higher than 60degC. However, the G3 Guidance Note 3.6 refers the reader to a publication issued by the HSE entitled HSC ACoP.
Temperature control is contained within Section 151 (Hot Water, Section B)of HSC ACoP L8 wherein it describes that hot water generating equipment (cylinders/calorifiers, direct fired water heaters etc) should deliver water to the hWS distribution pipework at a temperature no less than 60degC and with return temperatures (if applicable) at no less that 50degC. Branches from all HWS pipework must be designed to deliver water to outlets at no less than 50degC after one minute of opening the tap. Some establishments such as schools, care centres, hospitals etc are governed by regulations dictating the installation of Thermostatic Mixing Valves set to 43 or 45degC (dependant on the application and building), but the hot water entering the TMV must still be at 50degC.
Therefore heating plant thermoststas must be set to 60degC, not just once a day, not just once a week, but constantly.
Systems that have been idle for a week or more must have the temperature of the heater raised to at least 60degC for one hour immediately prior to use and the water circulated through the HWS pipework with the return pumps operational.
Hoping this helps.