Hi Rob,
To find out more about paying National Insurance while abroad please read the following
Social Security abroad: NI38 , the application form CF83 is also provided.
Within the NI38 there is full explanation of what class NICs are in the UK. There is also information about working abroad.
Each case is worked in relation to what information is held on the individuals NI record and what their circumstances are while abroad.
There are other factors that are considered like whether the country you are living/working in has an agreement with the UK, whether you are posted overseas by a UK employer.
You will need to provide as much information as possible include exact dates of employment or self-employment in the UK and or abroad and a list of all countries with exact dates you were living/working in.
Thank you.