Hi SJD,
No, you cannot get the final 9 months on the 2nd property as you have never lived in it.
As the will not complete on the same day, you need to report 2 different Capital Gains. when doing the 2nd one.
You have no annual exempt amount to claim unless the 1st gain is under £6000.
Please see:
Report and pay your Capital Gains Tax
Thank you.