Try and you are sure to find someone willing to ship.
A probable is:
http://www.bananas.com/index.asp/category_Guitar/subcategoryid_1
and click on guitar strings. Elixir acoustic strings on sale there.

Also try
http://stringsandbeyond.com/elixir-guitar-strings.html
They ship to UK.

Of course you are aware that your package may be assessed UK sales taxes and customs duties if applicable.