Hey @Deletedwood26
BT Mobile is a strange one (to put it lightly). So they went through a phase of saying their sims included 5G access, then they didn't (as a way of encouraging you across to EE) and then they did again.
It sounds like your sim does offer 5G as you've said yourself, you're getting coverage in and around Belfast. It just sounds like the other places you're in, the network Three offers 5G coverage but EE doesn't.
Then we come onto 5G roaming. Unless somethings changed, I don't think EE officially acknowledge that they offer 5G roaming so not only are they not shouting about it, it means you can't get an official answer as the internal knowledge management tools that their agents use with be like 'don't know what you're talking about'. We all know EE do offer 5G roaming, I too have had 5G coverage in the Republic of Ireland - lightning fast speeds on eir when in Dublin.
But then to complicate matters further, we have BT Mobile. It's always been operated as a MVNO (mobile virtual network operator) of EE and not a great one (in my opinion, I was a customer for about 5 weeks before jumping ship).
They never offered the same range of services (e.g. products such as visual voicemail or add ons) which basically is how MVNOs work. So whilst EE offer 5G roaming to eligible customers, their MVNOs may not which could explain why you get 5G when on the home network but don't get 5G roaming in RoI.
I know your daughter mentioned she had which could mean her sim is set up differently but I don't think you'll get to the bottom of it as it's a service that officially doesn't exist and as BT Mobile is coming to end of life, it may be worth checking out the deals available to BT customers (via the BT Mobile site) on EE next time you're upgrading.
As that way you know you'll get 5G when you're crossing the border.
