You asked

Do you have any statistics about the average number of non-resident pension beneficiaries, average amount of pension funds transferred to them or the percentage of whole pension beneficiaries which are non-resident?

We said

Thank you for your request. The requested information is not held by the Office for National Statistics. To the best of our knowledge, there are currently no official estimates of the kind requested for private pensions. The Department for Work and Pensions (DWP) should have information on numbers of non-resident state pension beneficiaries. DWP may also have data on the amounts of state pension benefits paid to overseas residents.

https://www.gov.uk/government/organisations/department-for-work-pensions