[Nextgrid]

Check out Andrews & Arnold. They provide real 07 numbers that aren't classified as VoIP by most providers, so they will actually work fine for most online services too.

(my company resells these with some add-on services on top, but for your use-case you're better off just going to the source directly)

[bpye]

I was tempted by this but I've heard they'll shut down your service if they figure out you're outside the UK? I still have a UK number at the moment but if I could port to A&A without worrying about this I totally would.

[Nextgrid]

Maybe just reach out, they take pride in their support and are very accommodating. If their concern is about payment, you may get around that by offering to prepay for a year's worth of usage upfront.