Your budget of £10,000 is certainly enough to get a good quality family estate car that is reliable and durable. The makes you mention are all excellent quality too and thoroughly engineered, making them ideal for long term ownership. You can get 2005 Audi A4 which would be our recommendation, ideally with the 2.0 TDI engine. The 1.9 TDI is quite noisy and not as good to drive, while the 2.4 petrol is thirsty. S-line models look good and are better in corners (thanks to sports suspension) but this does mean a firmer ride, so if you're after comfort it may be best to go for an SE trim. If you're after something larger then there's the A6, E-Class or 5 Series - plus the Volvo V70 is worth considering.