Firstly, a BMW F30-series forum which may be able to help you out. The UK section is particularly lively.

f30.bimmerpost.com/forums/

Though they're just as likely to be able to find you a way of getting a brnad new car for incredible levels of discount. There is one (in particular) person in sales at a BMW dealer who will probably leave you astounded at the deals that are available buying new.

They are, all told, very different cars in terms of useability. I've got a 325d tourer, (and had it for nearly 2.5 years now) and it suits what I want out of a car perfectly. Whereas a GT, with the boot lip and the sloping boot lid, really wouldn't.

So what do you NEED a car to do. If pram / pushchair duties then the tourer wins hands down. If it doesn't matter, then the GT or even the F30 saloon might well fit your needs.