@nhkyn ,
1. Since your pension is from National Health, is this public funds pension -- this is because most treaties , including UK, publicly funded pension and/or social security equivalent is generally taxable ONLY by the distributing country. If that applies here --- you should have some documentation to show whether this is true in your case --- then this income is taxable ONLY by the UK ( and therefore Tax at source ).
2. In any case for US 1099- R , the taxable portion generally is gross less recipient/employee contribution ( allocated or otherwise ).
Could you confirm that your employment during those years was for the NHS -- and therefore the pension should be marked as public funded. And not for a private hospital system.
