[Washington]

The back tyres are at about 7 mm and the front at 3 mm.

So do you reckon I should just bite the bullet and get two new Pirelli's and just get them to swap the rears to the front ?

I'm always wary of Italian goods   I flucking hate tomato's 

Sounds good to me especially for only a month between getting all 4 matched. With new tyres you might want to get the alignment checked too so you know they will wear evenly.