Are you going with carry-on? If so:

- SUNSCREEN: We take tiny travel-size sunscreen. You can get samples at the dermatologist or buy the 1 ounce size at CVS or any large drugstore.

- REPELLENT: You can find Ultrathon, excellent hands=free Deet repellent w/ a sponge applicator at REI or Magellan's: http://www.magellans.com/ultrathon-w...nge-applicator - less than 2 oz.

I always take a small DEET-free kind as well, lots of choices at any camping store. Mr. Crosscheck likes DEET wipes, which take up no space, but I don't like the repellent to touch my hands: http://www.amazon.com/Tender-Bens-12.../dp/B001GAOIME

If you're stopping at Heathrow, there is a great DEET roll-on at Boots.

I wouldn't stress too much about this - all will be available there.