Micra 1.0 fuel consumption

Hi all

I get around 30mph doing short trips in London. Shouldn't I get a lot more?
The engine sounds ok and only has 63k miles.
(I was a mechanic many years ago.)
I fitted a different s/h "computer" when I lost my key - no difference.
Any ideas out there?

You sound really expert. What mpg should I get?
Spark: look at the plugs?
Vacuum where?
Timing - I'll check.
I actually get what Nissan says it is 14,4 kilometres and I've been at 15,2 and 14,2 and no speedometer tolerance, actual miles, want to know more, PM me can show you proper spark just compare, for vacuum it is not so hard just get some fitting replacement rubber hose and do not check for worn, just replace if never done before. For timing, you will need to put ecu in timing mode so just don't touch idle screw and mechanical ignition advance yet or you will mix up ecu and it will run weirdo
thanks - what's 14.4km?
I'll start with vacuum pipe to throttle - idle is a bit erratic so that sounds right, then take a plug out
I don't have control over ECU
Hi richardwbb - there's no distributor.
Vacuum: the fat one from the brake servo to the "carb" looks very good - are there any more?
There is a little rubber pipe on the right coming up from the clutch? which connects to nothing like a breather? is that normal?
That's a gearbox breather, goes up but then connects no where so it doesn't suck in water.
There's a suction line goes from the throttle body to a valve on the gearbox end of the head that opens once hot, other end should be connected to the carbon canister might produce your symptoms.