I cannot comment on the UK side, but have you considered and addressed your green card abandonment issues for the U.S.?

As a lawful permanent resident, you are required to physically reside in the United States, except for brief trips abroad. However, there are any many lawful permanent residents, who, for a variety of reasons (i.e. family, business, employment), have a continuing need to reside abroad and enter the U.S. infrequently. However, their intent is to maintain their permanent resident status and eventually resume residency in the United States.

Therefore, those lawful permanent residents should be mindful of the fact that their permanent resident card becomes technically invalid for reentry into the United States if they have been absent from the United States for a continuous period of one year or greater. Additionally, even if the lawful permanent resident has absences shorter than one year, they may be considered to have abandoned their permanent resident card in certain circumstances (i.e. they have taken up residence in another country).

In order to avoid additional hassles at the time of entering the U.S. and to avoid loss of permanent resident status, the lawful permanent resident can file an application for a reentry permit with USCIS. The reentry permit serves as a travel document for the lawful permanent resident and demonstrates the lawful permanent resident's intent not to abandon their permanent resident status.

You can find good info on the reentry permit at:

http://www.familytousa.com/reentry-permit/

If you wish to hold onto your permanent resident status for the U.S., there are other considerations as well regarding maintaining certain ties to the U.S. etc., but the reentry permit is practically speaking a big step in the process.

I recommend consulting with an immigration attorney if you do not want to abandon your U.S. permanent resident status.

Regards,

Andrew M. Wilson, Esq.

Serotte Reich Wilson, LLP

www.srwlawyers.com

awilson@srwlawyers.com