Having read your column (http://www.honestjohn.co.uk/news/miscellaneous/2015-02/michelin-crossclimate-tyres/), when I needed to change just the front tyres on my Mazda 6 estate, I bought two Michelin Cross-climates, leaving two Michelin Primacy 3's on the back.
It has since been pointed out to me that this might not be the correct thing to hav done at all and I should really either have 4 of the Cross-climates or none.
Can I wait until I need to change the back tyres or should I change them now?