Everything is bigger so costs more (tyres, battery, brakes and so on). As a very basic guide, think what your Fiesta costs and double it. Check the road tax before buying, the youngest V6 190's are now £535 a year (if first registered after March 05 I believe).
Some parts are no longer readily available such as exhausts but stainless steel is an option, but will cost up to £600. As mentioned, buy carefully after reading the very useful buyers guide on here. Get one where all the expensive things have been done, pay top dollar for a good one and it will prove cheaper in the short run, let alone the long run
If you find a good one that requires little or no work it will still be far cheaper than some boring BMW or Audi. Plus you have this amazing club to come to for help and support plus the Facebook page. ENJOY..