On the US side, you will first need to find Part 1, which is located at the posted coordinates. Inside Part 1 will be the latitude half of the coordinates for both the US and the UK finals.
On the UK side, someone will need to also locate Part 1. Inside Part 1 on the UK side will be the longitude coordinates for both the US and the UK finals.
Once you have located Part 1 on your side of the Atlantic, you will need to find someone to trade information with. Try posting a note on the other page GC66YNT and see if you can find a partner. Once you have teamed up, then each of you will be able to find the final that you are searching for.
You may only log a find for the final cache that you physically locate. No “overseas” logging on these caches please. Also, please make note of the overseas partner that you teamed up with in your found log. You should also consider deleting your note from the cache page once you have teamed up with someone, so future cachers know to try and find someone else.
Once you have completed this multi, feel free to celebrate with a burger and fries, or some fish and chips, depending upon what floats your boat!