Recommend me a BMW 3 or 5 series- budget €17k

Timing chain is what you need to watch out for on these if it's the N47.

2014-2015 was around the time they changed to the more reliable B47 engine.

With the 3 series of definitely consider a 318d at a minimum. A 320d Efficiency Dynamic is probably the best for what your looking for.

Also don't think the early F30s or any F30 had reverse cameras.

OP, you seem to be looking for a unicorn in the current market. Used car prices have increased significantly since Brexit and on your budget and the brands you are interested in your going to be looking at cars with that sort of mileage which is not overly excessive for the year to be honest. With the budget you have because of increased prices your either going to have to accept dropping back a couple of years or accept higher mileage. Reliability expectation needs to be the same, these are premium cars approaching 8 or 9 years old that cost 40k/50k when new and are still that to fix so reliability is a mixed bag unless you go for something boring but less risky.

To summarise, your not going to get everything on your want list within budget - reliability, premium brand, age and low mileage. Your going to have to pick some of those and compromise on others.