I think you started the discussion, with wanting to run something cheaper. If you work out the average fuel cost for each model over 20,000 miles, the difference is probably about £1,200 in favour of the 2.4 (assuming 22mpg for the 3.2 and 30mpg for the 2.4)
Road tax will be £200 for the 2.4 vs £435 for the 3.2.
Insurance - probably not much difference.
So over two years, you will save £1,200 + £235 + £235 = £1,670 on fuel and tax.
But this 2.4 has higher miles, so possibly will cost more to maintain.
So assuming there is no difference in what you get for your car and what you have to pay for this 2.4, then is £1,600 a worthwhile enough saving for the lack of a V6 in your life???
But then I suspect there is a difference between the 2 in cost, ie you pay more for the 2.4??
I reckon you are just trying to justify a change of car. Nothing wrong with that - I do it all the time!