http://prepaid-data-sim-card.wikia.com/wiki/United_Kingdom
Following a referendum in favour of leaving the EU in 2016, the UK gave two years' notice to leave the EU by March 2019. The UK has not yet given the required one year's notice to leave the EEA, throughout which EU roaming regulations apply, as explained in the European Union chapter. Therefore the UK remains bound by EU roaming regulations for the foreseeable future.