I've seen a few auto box failures on BMW's at the 100k or so mark.
And a few large bills for new DPF's also, on cars approaching ten years old.
In fact, I've seen too many large repair bills on BMW's I'd steer clear, especially any diesel car with an engine management light on.
So a 535d would be off my list with a 10k budget. A shame because they drive insanely well.
I'd be looking at the Skoda Octavias, Golf estates, Passat estates.
I'd also be looking at petrols if I wasn't doing many miles per year.
Mercs are lovely, but I have very little sales experience with them so can't advise.
Tim
Ps, as for funding it, the likes of Tescos and Santander have sill low rates for personal loans, we've never been so lucky to be able to borrow money so cheaply.