Tier 2 Extension with renewed passport

Hi,
My passport was to expire in May 2016 but I have already got it renewed.
My current visa expires in Dec 2015. I will apply for renewal next month. My employer has already given me CoS. They have mentioned my old passport details in passport or travel document section. They have added a sponsor note in CoS saying that migrant has secured new passport with details.

Just a bit curious if this is OK. Should the passport and travel documents section not be filled with new passport details.

And, any suggestions whether I should go for premium service or normal one?

Thanks,
V.

it should be fine. U will be sending your old passport along anyway, and just to make sure they dont miss the sponsor note, you can add a letter stating that i have recently renewed my passport and that your employer has told you that they have added anote in cos as they are not allowed to amend the cos.