Better off buying a old banger that has as near to 12 months MOT as possible and running it into the ground. Cheapest option when you consider lease charges or depreciation costs.
Like everything else in life you pay for what you get.
Leasing a car: peace of mind, no maintenance costs, no worries about depreciation, known fixed costs. BUT you have to be prepared to pay more for the privilege.
Buying a newish used car outright; possible bargain, cheaper, but risks of getting a dud, repair costs, breakdowns, depreciation worry, maintenance.
So it depends whether the benefits of leasing are worth the extra costs. For some defintely worth it especially those who would like a newish model every 3 years.
E.g: for a 2 year old A6, deposit £4K, contract of 3 years at 250/month. So this is an outlay of £13k over 3 years.
If you buy it outright it would cost £20k and include finance etc it comes to 22k and then if you include servicing etc and depreciation, you would probably have spent £10K in 3 years if you are lucky.
So not worth the hassle. If you want a new expensive car, leasing is the way to go. The only exception is for the really desirable used car which does not deprecaite that much.