You got the car in February 2009 and told us in May 2009 the car had done 60k miles and it had the Zito wheels on then. You have not mentioned how many miles you have done since and seem to be saying you have not changed the tyres yet you say they are in pretty good nick - suggesting you have not used the car much and, shall we say, been gentle with the power
I would suggest you check the basics first - how much tread have you actually got left and is there even wear across the tread. Make sure the tyre pressures are 35psi, when cold.
Normally for 19" wheels, 245 at the front and 275 at the rear with the profiles you have are used, but the rather unique offset the Zito wheels (and rim width?) may dictate something else is warranted. But I have little doubt that your TC problems are down to the tyre/wheel combination and tyre wear over an 18 month period is the root cause of your TC issues.