The UK Government has launched a review of the UK’s IP laws, which will include consideration of whether we can learn from the concept of “fair use” in the USA. Fair use allows copyright material to be used in certain circumstances without the rights holder’s permission, and clearly any change is likely to result in a more flexible regime for advertisers. However Osbourne Clark suggest in their post that it will be several years before we see any change in the law.
On the down side, however, it’s going to be difficult to hijack the recently-announced royal wedding for marketing and advertising purposes. The ASA has issued strict guidelines, and Osbourne Clark’s excellent article on the regulation concludes with the following comment:

It is clear that referencing the happy couple’s nuptials as a way or reason to have a special promotion is acceptable, but be careful when producing items designed to commemorate the day.