If you exchanged contracts to sell your UK property by 5 April 2015, you would not have any liability to Capital Gains Tax in the UK because you are non-UK resident. That is, provided you have maintained that status since you left the UK in 2007. Take a look at HS283 here
for more information on CGT and the main home.
As you will read here
, from 6 April 2015, the UK government plans to subject non-UK residents to CGT on gains made on the disposal of UK residential property but
only on the difference between the disposal proceeds and the value of the property on 5 April 2015. The detailed draft legislation will be published after the Budget next week and that should bring more clarity.
You may still qualify for full exemption from CGT even if the property was sold after 5 April 2015 due to the absence abroad provisions which you can read about in CG65030 to CG65050 starting here
. As you will read in CG65046, both before and after your absence abroad, the UK property must have been your only or main residence and there must not have been another property which could have qualified for the main residence exemption.
I hope this helps but let me know if you have any further questions.