Just been reading some more online and found this, which suggests that i will need to have a output voltage the same as the input voltage and i will not find a VFD/Inverter >3kW ?
"• Inverter manufacturers do not offer product for single-phase supplies in excess of 3kW to ensure
compliance with European Power Quality Standards such as BSEN 61000-3-2:2006 and BS EN 61000-3-
12:2005. For similar reasons inverter manufacturers do not offer product with an output voltage that is
different to the supply voltage (e.g.: 240v input, 415v output).
"