How much should I budget beyond the price of a used car?

The purchase price is not the whole cost. Budget for the following on top:

• Insurance — by far the biggest variable, and worth getting quotes on the specific car before you commit. Insurance groups vary enormously between trim levels of the same model.
• Vehicle excise duty — depends on CO2 emissions and first registration date. Since April 2025 electric cars pay it too. Cars with a list price over £40,000 when new attract an additional rate for several years, which catches out buyers of used premium models.
• Fuel or charging — the largest running cost for most drivers.
• Servicing — budget annually, and check whether a cambelt or major service is due soon, as those are the expensive ones.
• Tyres — a set can be a few hundred pounds, more on larger wheels. Check tread depth at purchase.
• MOT — annually once the car is three years old.

Two costs specific to where you drive: the London ULEZ daily charge if your car is not compliant, and the Congestion Charge, which is separate and applies regardless of how clean the car is.

A sensible rule of thumb is to keep something back for the first year rather than spending your entire budget on the car itself. Any used vehicle may need tyres, a service or a wear item sooner than expected, and having a margin turns that from a crisis into an inconvenience.