If you don't have ipv6 internally, you probably can't access ipv6 externally. 6to4 gateways are a thing. 4to6? Not so much.
And this is why ipv6 will ultimately take another 20 years for full coverage. If it was more backwards compatible from the starting address-wise then this would all have been smoother. Should have stuck with point separators. Should have assumed zero padding for v4 style addresses rather than a prefix
Prospect in the UK