This will be the UK's (and my) loss
Their customer service is MILES beyond that of their competitors. I'm a T-mobile customer in three countries (UK, Germany, USA) - and in the UK & US, have had complex matters to deal with. They have been generous and efficient in resolving problems. [I have no vested interest here; just a really happy customer that does not want to see them go]. Have been with them in the UK since the One-2-One days (still using the old blue SIM-card!)