CGT help - for non-resident

Hello,

Can anyone assist me with working out the CGT liable for our leasehold flat in London?

Mid 2006 – bought 40% (shared ownership) and lived in as main/permanent residence (total purchase price was £175,000)

2008 – upgraded to 100% share, and lived in as main/permanent residence (total purchase price was £227,500)

April 2008 – moved to Australia and have rented it out ever since

Current value approx. £285,000

Does the shared ownership issue affect CGT?

Are non-residents liable for CGT in the UK after a certain timeframe? If so, how do we calculate the rate at which it is taxed? Is it based on our Australian income? Also, how do we calculate the amount to be taxed?

If not, do we have to pay CGT on the profit here in Aust?

Thanks,
N