Yes you can go to any authorised dealer to have your servicing done. Check with BMW before sending to your chosen dealer.
No, there is no program currently to renew or extend your BSRI once it expires.
Beware, the BSRI program will entitle you to an oil change following the car's computer which would be between 25-30K km. Off late, dealers have recommendedto do oil changes every 10K km. This will be at your own cost since it is outside the BSRI obligations. Many here would pay for the additional oil change to avoid long term problems.
Be reminded that the BSRI time will always start from date of car registration and not from the date of purchase of the BSRI program. I found out the hard way.