Time I'm allowed to stay in the UK?

[wtmlive]

I recently changed employers and got m first BRP card.It states the date of expiry as July 2015. My COS for my new job was for 6 months only (uptil December 2014).

Did they make a mistake by giving me extra 6 months leave on my card? Can I live in the UK until July 2015 or work for the same sponsor without applying for a new visa? Or do I have to apply after December 2014 regardless of what my BRP card says?

[iworker]

Normally the visa is given for time on the cos plus 2 weeks.
U can continue to work for same employer until end of the visa, and can apply for an extension any time before your leave expires.

[manci]

your sponsor is not allowed to employ you beyond the work end date stated in the CoS