What I have found to be best for fuel economy is to make sure it is properly serviced, all filters are changed, premium quality oil, fresh diff and gearbox oil.
Also pay attention to the tyres you have, perhaps have some high quality road biased tyres for the week and get some more aggresive tyres to use when playing.
Use good quality fuel. From experience I found that BP ultimate, even though it is more expensive than supermarket fuel, pence per mile it works out cheaper as you can can go further on a tank.
And finally, its not just a light tread on the go faster pedal it is also anticipating when you need to slow down. Using brakes wastes energy, the less you have to use them or come to the stop, the less fuel you will use getting back up to speed.
On my 90, yes it is a Puma I get about 34mpg but by using the same techniques I used to get 20+ out of a disco 2 V8 auto and 25-28mpg out of a disco 1 mpi.