The reason the National Television Awards have a slight broadcast delay (wasn't that long) is in case anybody accidently swears and they can bleep it out quickly - just like they do on I'm A Celebrity... Get Me Out Of Here, Big Brother, The ONE Show, Loose Women, Paul O'Grady Show, Alan Titchmarsh Show, The Bill Live and in Februrary, EastEnders Live.
The only programme which is broadcast live, and not 'as-live', which has to be by law, are the National Lottery Draws. The Euromillions Draw does not have to be broadcast live in the UK, but does in the country of origin (France).
You can find out more about broadcast delays here:
http://en.wikipedia.org/wiki/Broadcast_delay#United_Kingdom
The reason for the delay is to comply with OFCOM's Broadcasting Code. In 2005 the BBC said that as part of their editorial guidelines there would also be a delay on sensitive news (see
http://news.bbc.co.uk/1/hi/uk/4121406.stm ).
Even GMTV has a broadcast delay of around seven seconds!
Broadcast delays on Internet and mobile-based TV channels (such as BBC One Live on iPlayer, ITV1 on ITV Player and via TVCatchUp.com) also have to have a delay in case adverts cannot be broadcast on these platforms. If you watch ITV1 via Vodafone, Orange or '3' TV you'll notice that some programmes, films or adverts are replaced with a static 'ITV1 will be back shortly' or promos for programming because the said show cannot be broadcast via the Internet.
I'm sorry - you're completely wrong on this. The One Show, all network news bulletins, and shows like Strictly, are almost universally broadcast un-delayed live (when live) - though of course pre-recording sequences that cannot be achieved live has always been a production tool (though this isn't a delay, it is a pre-recording - the transmission of the item takes place after the recording of the item has finished).
Similarly only a very few live contributions from News events are delayed - and those that are should never have "LIVE" on-screen over them. (When two live events happen at the same time it is possible to delay coverage of one until the other has finished, rather than crashing into the second mid-way through)
Any delay that is present on theses shows is entirely the result of the transmission path (some compressed circuits introduce a GOP delay which can be 1/2" to a couple of seconds) and is not for compliance purposes. The transmission path varies widely depending upon how you watch. Analogue off-air in London is almost delay-free, whereas Freeview in some areas may be much more delayed, as is satellite.
The delay on many streamed services is mainly a result of compression and buffering - certainly there is no compliance related delay on BBC One, BBC News etc. when streamed to the web or mobiles - the delay you see is merely a result of an additional compression stage, the delivery to a CDN (Content Delivery Network) and then the local player code buffering prior to replay. Some streamed services actually source their video from satellite or freeview off-air receivers, so their source is already delayed...
Some "live" shows may chose to use an additional delay for compliance reasons (if there is an issue of control over a guest who is widely known for swearing), or for security in case something goes wrong (such as a live drama) - but many live shows still don't.
Your suggestion that most live shows, apart from the Lottery, are delayed for compliance reasons is, I'm afraid, totally wrong.
There are also some shows that are broadcast with much longer delays to allow editing. The BAFTA awards used to go on-air a good hour after they'd actually started, but before they'd finished. The production team were thus able to cut-down some award acceptance monologues, so that the final show took up a shorter time-slot (and again they could remove bad language or legally contentious comments etc.) than the actual event (and was less boring to watch). However this is a very different sort of delay to a 15"-1'00" compliance delay.
Most live galleries I've worked in still watch an analogue network or off-air feed to see themselves go on-air, which is normally only a few frames delayed...