Cars don't make a massive price difference anymore for insurance if you stick around the 1.2 petrol or 1.4 diesel mark, and providing it's a 3 door hatchback; add a turbo then you're asking for trouble, make it a saloon or anything bigger the same applies. You're paying for damages and injury you can cause to someone else, and that's why you're usually going to pay more than the cars worth for your first year.
The issue is you have a genuine need for a bigger than average first car, and you're just going to have to take the insurance hit, I'd suggest a Ford Focus, they're roomier than most hatchbacks.
My advice to you is don't bother with an estate, as confident as you are an easy to drive hatchback is the best plan for your first year at least. I've been driving 2 1/2 years now and I'm driving a 1.2 Clio (yr 2000). There are times when my inexperience on the road has been saved with this car being so nippy. I don't drive fast by any means but when you pass your test and you're on your own, your decisions can sometimes be the wrong ones, and it's usually caused by panicking and compensating for other peoples mistakes....and I say mistakes but it boils down to bad driving through bad habits.