Another Honda, Volvo, Subaru legacy, Audi - that kind of thing. Petrol is better as I have a better chance with the LEZ, and a flat loading bay is also desirable.
King of the hill would be a Honda CRV - I luv'm and I think they might do a petrol version (need to check that).
Quite sadly, 'station wagons' as we call them in the US were largely discontinued and replaced with SUVs here in the US by the turn of the Millennium. :S Thus, it's hard for Klassik to make any recommendations which might be useful to you. The most reliable car on US roads from the early 2000s, which would probably fit your price range if you were in the US, would be the Toyota Camry XV20. Klassik does not know if the Camry XV20 was even sold in the UK. If it was, it was surely not common. That said, maybe there is some other similar Toyota which is more common in the UK.
The Subaru Legacy is still sold in the US in 4-door form. Klassik would avoid Subarus from the 2000s and early 2010s. The Boxer engines they used at least here in the US during that time have a terrible reputation for head gasket problems.
Many cars from the 2000s still used timing belts instead of timing chains. If the engine is an 'interference' engine design, if the belt slips, the engine will be ruined so it's critical that the timing belt is within the specified service life of it. Timing belt replacement service is not cheap and so people with cars not worth a lot often neglect this. In totality, the maintenance of whatever car you buy is going to be important. If you can find something that has been maintained properly and regularly, it'll likely be a much better buy than something that hasn't been maintained properly. Some cars handle abuse better than others, but there are limits to everything.
Given your price range, you're likely to be buying a car from the time period where air bag recalls were common at least here in the US. Hondas in particularly were prone to air bag recalls, but they're hardly the only manufacturer who had to replace air bags at least here in the US due to safety problems with the inflators as they aged. Some air bags had a problem with spewing metal shrapnel when they inflated as they aged.
Klassik knows not how these air bag problems were handled in the UK. If there were recalls, make sure the recalls were done. Also, do some research and see if the replacement air bags will also need to be replaced at some point down the road. There was some concern that the replacement air bags may have the same problems as the original air bags. Klassik knows not about that.
Klassik quite hates crossover SUVs as mentioned earlier, but the early Honda CR-Vs were pretty reliable. Newer ones have problems especially with fuel getting mixed into the oil on the ones with small turbo engines which causes the oil to degrade quickly. :doh: The biggest problems with Hondas from the 2000s and early 2010s, aside from the air bag problems, are troublesome automatic transmissions though most of these cars in the UK probably have manual transmissions anyway which should be fine. At least here in the US, some Hondas in the 2000s switched to using very small batteries which are prone to having starting problems if they aren't given sufficient time to recharge from the alternator. Also, some Honda engines from that time have issues with excessive engine oil consumption. Klassik's former 2009 Honda Accord with the K24 engine did have oil consumption problems, but only when the car was driven fast (70+ mph) on the highway. If kept below that, oil consumption was negligible.
Klassik does have personal experience with one 'wagon' which might be in your price range, the B5.5 VW Passat with the 1.8T turbo 4 cyl. engine. What a piece of London that car was. The car was only around here for ~50,000 miles, but it needed around 10 major repairs during that time. It couldn't go more than about 10,000 miles without needing new ignition coil packs (a known problem on those cars). That's just to mention one problem. Klassik would avoid any car with that engine (they probably did also show up in Audis, Skodas, SEATs, etc.). Klassik does not think the Passat was all that well-built otherwise, but certainly the engine was the worst part. Perhaps it would have been better with a different engine.