We bought the Cruz roof bars from
https://www.roofbox.co.uk.
Originally for our Mini as it had roof rails already. Once we bought the F30, I just spent another £25 on the specific roof bar mounting brackets for that model and we now have a roof bar system we can use on both cars without needing two separate sets of bars.
Roof box we went with the Kamei 510L which was expensive at over £400 but its massive and I am glad we went with the bigger one. Two person job to get on but just sits in the garage when unused.
Edit - Just realised this is an old thread. Never mind!