I have the 1.8 FL1. Routinely getting over 31 mpg and can get better with a little effort.
My mod's were done when I had the head... off, they include:
clean out all plastic flash left over from manufacture in the inlet manifold, ditto for the exhaust manifold and front pipe, clean out weld splatter & sharp edges that protrude from the metal pipe.
Head work: open up the inlet and exhaust runners, port match the exhaust side, smooth out the valve throats as the valve seat often protrudes out of the casting [just smooth / round the lower edge off], round off the valve guides, unshroud the valves in the head - you could get as much as 2mm but 1.5mm is safer, back trim the valves just a whisker. de cat it? fit a K&N Apollo air filter and a cold air feed too. New plugs, rotor and duster cap if you have the earlier mems 1.9 ECU & motor.
Check tyre pressures, clean / replace air filter, Run good quality fuel, replace fuel filter, run injector cleaner through the fuel system... don't cart round superfluous baggage - take the cross bars off the roof rails.
Use it & enjoy it.