Before you look at cost, decide what you want to do with your aircraft. Owning outright is an expensive option in most cases. Having said that, an aircraft is like any luxury item. You buy out of choice because that is how you want to spend your money. You will not break even on cost unless you fly more than most of us can manage. Hangerage and insurance alone will be £80 per hour + if you fly 50 hours a year. Fuel will be £20 + per hour depending on type of aircraft, avgas or mogas. Then if you buy something relatively new there is depreciation and lost interest on the money which would otherwise be sitting in your bank.
Maintenance of a C of A aircraft will be around £2k per annum as a minimum; a permit airctaft may be as little as £3 - £400.
A combination of group ownership and hire can actually be a good option and will give you the possibility of having a variety of aircraft at your disposal.