I need to get rid of my MG ZT-T CDTi and get something much smaller and more economical as I am commuting 500 miles per week between Warminster and Weymouth - all A roads with a few miles of dual carriageway - and the 43mpg I am getting from the MG is a little too low.

The car only has to carry me, doesn't have to look pretty or a desirable colour and I don't have a huge amount to invest on top of the value of the larger car. Is there anything out there that will do starship mileage economically and reliably? And do I want to be looking at cambelt or cam chain engines?