PS: Does that mean that the laws tracking over uk airspace have been relaxed.. as some time ago one could not do that, unless you have your own AIrNav system.
They way that I had it all explained to me was something similar to ...
Those Airnav/radar-box/whatever trackers are using the signals transmitted by the aircraft themselves; some/many of the signals include the lat/long of the aircraft, and the program uses this data to plot their position and track on a map. The nature of the aircraft transmission is that it is a 'broadcast' (that's the 'B' bit of the ADS-B acronym), so the signal is available to everybody - those who it is intended for, and those not.
On the other hand, the voice transmissions from ATC to aircraft, and vice-versa, are destined for each other (and, to a degree, other aircraft on a given frequency). They are not 'broadcast' and therefore not available to everybody.
Hence, it you re-broadcast (across the Internet) the audio from your ATC scanner, you are breaking the law. However, if you re-broadcast a signal which is already defined as being 'broadcast', you are not.
Having said that ... when you look at the Internet and see a map of (say ...) the UK airspace and see a number of 'blips' moving around, you're not actually seeing/hearing the bradcast signals, you're seeing the results of a computer program which is interpreting the signals.