Well, you're living in Newcastle so the obvious places to ask are Newcastle airport (some GA, but expensive) and other places like Eshott, Fishburn. Call them up and ask how much hangarage and landing fees would be. It'll take you an hour. You could do the same for insurers and ask for ballpark quotes. You won't need to pay airways fees if you're flying VFR as a PPL.
Fuel costs: look at how much fuel your chosen aircraft drinks per hour. Look up fuel prices, and multiply.
Maintenance costs are an issue - perhaps someone could give a ballpark figure for what the annual costs on an SR20 are likely to be (used or new?)
The formal syllabus doesn't include GPS (as far as I'm aware) but there's nothing to stop you getting someone to teach you to use it, if you need to.
You may be able to get someone to teach you on your own aircraft, so why not buy it before you complete your PPL? That would solve the 10 year issue. Why is it so important to you? Safety? I wouldn't worry myself.