Turn your a/c off, switch to Econ unless it's unbearably hot. Coast where safe to, and use predictive driving; don't accelerate when you've a queue or bend ahead and you know you'll have to brake etc.
I generally don't go above 2200 rpm, and that's where all the power is anyway.
I'm a speed freak, but now I'm and mpg freak!
I love a/c too. In some big engined cars I've found it makes little difference to MPG, in the 1.4TDi I've found it does indeed make a difference, even at temperature and at speed.
I treat the MPG as a constant challenge, and only build speed when I know I won't waste it, keep it once I have it, so pee off those behind me and then pass them on the bends kind of driving. It's a challenge.
I don't drive over 60mph on the M'way or A roads either.