Hi Hobo,
Gretchen Becker, a resident expert here, wrote about her travels domestically. While she did not travel out of the country like you are planning to do, she does have some tips and experience that you might find helpful. You can read the article titled "Traveling with Diabetes" here.
Mary Kate Cary has also offered some tips for traveling here in her article called "Spring Break: Tips for Traveling with Diabetes". Among other tips, Mary Kate Cary advises, "Bring enough snacks to survive a long layover or a missed flight - or
more likely, a mad dash between planes with no time to eat a full meal.
With fewer and fewer airlines serving food on board, don't count on
getting something to eat on the plane. Have plenty of food with you
that doesn't need refrigeration."
Hope this helps!! Enjoy your trip to London and let us know how you are doing and most of all, let us know how the trip went!Vicki M