After this post I tried getting in touch with a rep of Signet, I didn't get through to anyone since it was a weekend. I will try again and post my experience of what they say here in this thread or create a new post if there are some important things to share. It's just that I'd feel pretty awkward pretending to be a hopeful retail customer for them, never window shopped banks before ya'know..
Keep us posted. I assume even the most crypto friendly bank will have made their existing clients jump through a million hoops before deigning to business with them. A cold call will probably earn a chuckle at least.