When downlighting is desired the best solution is often to replace the whole 12 volt MR16 fixture with a new energy efficient recessed fixture.
The advantages are
Energy efficient fixture are available for both LED and CFL globes. If the existing fitting was plugged through a standard power point then teh fittings can be installed yourself, otherwise an electrician will be required to remove old fixtures and to wire in fixtures.
Alternatively a 12 volt to 240 volt adaptor can be used to allow the fitting to fit a 240 volt globe.