We really need to know your budget to give you specific advice on which cars to look for, it's very difficult to without. With safety a key concern we would not advise looking at pre-2000 models when crash safety requirements were pretty lax. The usual suspects include the Ford Fiesta (fun to drive and cheap to run with the 1.25-litre engine), Vauxhall Corsa (also cheap to run and loads about) and Toyota Yaris (strong reliability reputation). As VW Polos command a premium you might be better off looking at the SEAT Ibiza or Skoda Fabia, these use the same engines mechanicals as the Polo underneath. Older generation cars can actually be more affordable to own due to their simplicity, while a well looked after model with plenty of history should mean all the key failure points of the car will have been taken care of. An older model that's been taken care of with lots of receipts is a better bet than a newer model that has high mileage and hasn't been looked after.