Welcome to FT flyer_berlin

As far as I know the *A offer to UK residents (at least have UK address ) has been closed for some time.

If you have only LH miles (& upgrade certs?) then you can upgrade easily on LH/LO/OS/UA. For other carriers you could try paying extra at check-in (probably quite expensive for a RTW if it is accepted at all) or hope to receive an upgrade voucher from someone who is in that carrier's FFP in exchange for something else you can offer them). On certain carriers you may also be lucky and get an op-up.