In all likelyhood, the UK would either change nothing, or possibly increase its own defense funding. They might also drop their opposition to the creation of a European army. Taxes (which are too low in the UK compared to mainland Europe, anyway) could go up a little to pay for this. All in all, nothing to worry about.
Japan arrests U.S. activist featured in award-winning documentary 'The Cove' (DPA)
from the article: Israel may ask U.S. for $20 billion more in security aid, Barak says