Capital Gains Tax on property taken over from ex

My ex bought a property in 2000 jointly with his ex for £25000 and then in 2008 he bought his ex out of the property at the time of their divorce, for £100000. Now we are getting divorced and I need to know that what will be the bought price when calculating the CGT now if I take over the mortgage off him

Hi,
His acquistion cost is 50% of the cost in 2000 and the sum paid to buy out the ex's 50%.  The mortgage has no relevance, when calculating capital gains tax.  How the acquisition is financed does not factor into any capital gains calculations.
Thank you.