There is no time limit, so all treatments since 2014 may be considered.
It is important to have documents proving that a patient was an ordinary resident in England during the time of treatment in Europe. A permanent resident card or British passport is not required. It is sufficient to submit a bank statement, where it is clearly shown that the patient lived in the UK before and after treatment and one document directly related to the place of residence: council tax, utilities, HMRC account or a copy of the rental agreement.
A driving license, mobile phone bill, payroll/work permit are not normally considered documents proving permanent residency.
You must also be registered with your local GP.
We would like to emphasize that during the Brexit process there are no planned changes to this scheme.