Thank you for your patience ..
In the absence of your reply on month of purchase and sale, I have made these assumptions in my calculations ..
date of purchase - Jan 2003
date of sale - Dec 2014
The good news is there is no CGT payable as all gain is covered by private residence relief and letting relief..
You have owned the property for 12 years and 9 years are covered by private residence relief. In additional there is a relief for a further 18 months called the final period relief
This leaves you with approx 18 months period that is chargeable for CGT purposes.
As the property was your main residence before you let it, you get letting relief up to a maximum of £40,00. The gain applicable to 18 months is only £13,125 and this is covered by letting relief.
I hope this is helpful and answers your question.
If you have any other questions, please ask me before you rate my service – I’ll be happy to respond.