As far as the conversion is concerned you may be pushing the preverbial up hill given the age of the cooker. You will already know that Metters no longer exists as a gas cooker manufacturer well at least the cookers that we all once knew anyways. There is a problem trying to convert from Towns Gas to LPG gas in particular the valve inside the control taps as they will currently have quite large bypass ports in them and if used on LPG fuel will NOT allow sufficient “turn down” of the burners to be of any use other than on “full” control. Another problem will be the oven thermostat which will require modification by way of the bypass or turndown jet which again will be far too big and will cause the oven temperature to continually rise rather then regulate down at the correct temperature. Once again the grill burner will also be a difficult challenge.
In all I don’t beleive what you are asking is actually achieveable well not economically at least. Sorry I can not be the bearer of better news for you.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians