John, thank you for your prompt reply..
Lets say the property is sold in Aug 2014.. you would have owned it for 8 years (96 months)
The period to Sep 2012 is covered by private residence relief.
The period Oct 2012 to Mar 2014 is covered by additional relief available (final 18 months of ownership provided the property was main residence at some point during the period of ownership) - upto 5 Apr 2014 the final period was 36 months.
You are left with period from Apr 2014...
As the property was your main residence and it was also let for a period, there is a further relief available called letting relief. This ould wipe off any gain left after adjusting for the two reliefs aforementioned.
You will have no CGT payable on sale of the property.
More information on private residence relief is covered here
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.