Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question,
Firstly, when you left the UK did you complete a Form P85 and send it to HMRC? If you did not you should do so immediately. Fortunately there is no time limit as to its submission, it is available on the web and can be filed on line. On receipt HMRC will classify you as non resident. Once non resident you may spend up to 91 days in the UK each tax year without breaching your non resident status.
On return to the UK you advise HMRC and they will split the tax year of return into two parts, one non resident and the other resident. Assuming you sold whilst non resident there would be no liability to UK taxation, but you should warn your UK bank of incoming funds and their source to preclude any money laundering enquiries a large sum might attract. The NZ tax system has no Capital Gains Tax (CGT) regime save for some specific investments.
In the unlikely possibility of HMRC trying to apply CGT to you, were it your sole or main domestic residence, then Private Residence Relief (PRR) would apply which relieves UK CGT at 100%.
I do hope that you have found my reply of assistance.
Thank you for your support.