Hi Anna,
Am I correct in assuming the house you're selling was the "old" one which you've been renting until it sells?
My first take would be that CGT shouldn't be payable on the first house as long as it is being sold within 12 months of you moving out.
CGT is not normally payable on your principle primary residence, and there is an allowance of 12 months from the date you move out during which the original house would still be considered your PPR.
The fact that the house has been rented out for 2 months shouldn't affect this additional 12 month PPR consideration.
Your best bet would be to talk to the solicitor handling the sale, who should be able to confirm if a CGT liability exists.
Charlie