Hi Sheila,

The A1 diesel is generally reliable and robust, but it (and the A1 in general) does have a few known issues that are worth looking out for. Specific to the diesel, if the glow plug light remains illuminated, it means a programming issue with the engine control unit. Also, make sure there is no problem getting fifth gear without an unusual noise. If there is a noise, best to walk away from the car as the gearbox could be expensively damaged. 

Other than that, check every single electrical system, including keyless entry, climate control etc.