Welcome Ian, i owned two 1.6 turbo Diesel's, and am fond of that little motor!!
But my elderly Father drives a new (2years old ) GD with 1.8 petrol auto it performs ok in the city just lacks torque, the auto trans masks the lack of torque by shifting down a gear quick & smoothly. I have not driven it in the country (open roads) it uses a lot more fuel than my diesel i30's did in the city. But the petrol very smooth runing for a 4 cyl motor, it uses cvvt so that part of tune could possibly be re programed to work in with re map of fuel & ignition to taylor performance. Other wise just improving exhast flow air intake flow could help along with changing the diff ratio to suit your driving conditions. But it all costs £ or $ . In tge end could probably look for a different car with more go. But always fun improving what you have .good luck