Well, no matter what you'd bought, the servicing /tyres costs, and the insurance/VED costs would have been roughly the same. The only way in which you would have saved money is with fuel - if you'd gone diesel. But then, the car would have been more expensive (probably), so any savings would have been lessened by that.

Unfortunately though, you're now at the point where you'll need to start looking at what it needs spending on it to keep it running, compared to sinking that money into something else. Do you run it for a year and then sell it with running out MOT, or get shot now with 12 months MOT.