My ZS is in its 8th year of ownership with me and I am not parting with it, nuff said
For what it is worth a remap is worth the money as economy is slightly improved overall, expecially high up when you need it the most.
If you are covering alot of miles over a month then work out what your budget is, what the ZS 180
should do and what an alternative may give you. You'll find there won't be alot in it when you compare running costs. Also factor in the underpowered cars performance and how hard you will push this along and this will affect its book mpg figures.
If you are one to have fun and drive it like you stole it then it won't matter what car you own, you will still not attain the books mpg figures.