You must have an amazingly heavy right foot to only achieve 33 mpg - I'm getting 32.5mpg from my petrol Leon FR!!
Yeah, I said that. with the 1.4 75ps you have to put your foot down to get anywhere, that's it's problem - It's too underpowered for it's weight, hence the poor consumption figures.
On a long motorway run I'll manage around 40mpg or so, but day to day driving and commuting I get 33mpg or less.
That said I only used to get 28mpg average out of my Mk 4 Fiesta 1.4 zetec - but that was a lot faster than the Ibiza.