Thanks you so much for the information. This is exactly what I was looking for. I have made numerous calls to USCIS and could not get this information from them. We have orders to the UK for Sept do I need to file any paperwork here or should I wait until I get to the UK?
Technically, if you want to use the provisions of CFR 211.1 (a)(6), you don't need to file any paperwork, either now or after you get to the UK.
However, it may still be a good idea for you to apply for a reentry permit anyway, even though it will be valid only for the first two years. Traveling with a valid reentry permit is easier and less of a hassle than with an expired green card, in case you need visit the U.S. before the two years.
If you do apply for a reentry permit, you should file the application (USCIS from I-131) before you leave for the U.K., since an I-131 may only be submitted while you are physically present in the U.S. On I-131 you may specify that, when the reentry permit is ready, you want to pick it up at a specific U.S. consular post abroad (e.g. the U.S. embassy in London).
I would also very much recommend that, once you get to the U.K., you explore the expedited naturalization procedure under INA section 319(b), mentioned in jackolantern's post.