Driving less than 15,000 miles a year does not warrant a new diesel car because of all the expensive things that can go wrong with them,
especially when driven short distances from cold. Potential problem areas are:

Diesel particulate Filters: £500 - £6,000 (if the engine blows as a result of malfunction)

Inlet swirl manifold actuators: £500 - £6,000 (if the engine ingests one and self-destructs)

Exhaust Gas Recirculation valves: £200 - £300

Turbos: £750 - £1,500

Intercoolers: £300 - £500

Injection pumps: £1,000 - £2,500

Injectors: £100 - £2,000

Dual Mass Flywheels: £800 - £1,600

Older diesels don't have so many problems.