I usually feel out of depth in the car thread, but as my last 3 cars (in order) have been an e91, an Octavia and now a V70 I feel I should probably contribute.
The BMW was the nicest to drive, but the boot is surprisingly tiny - Getting bikes in is more of a pain than it should be. It also cost a lot to keep going.
Octavia boot is amazing considering the size of the car. You'd get a decent one for 4k as well. But I never liked driving it very much and it had issues that made keeping it a bad idea (don't get a 1.8TSI). But if you want a large boot in a small estate it's probably by far the best option.
We then got a 2008 v70 for a very good price and so far it's absolutely great.Boot is really good, though it also has a towbar so I got a rack for that Holiday car packing rage (have two children and lots of luggage/bikes) is now a thing of the past. It doesn't feel that big to drive. Not particularly cheap for VED or fuel, but so far have had zero problems with it. Drove to Scotland and back in it recently and was great on motorway.