Apparently, UK radio stations can either opt not to allow people outside the UK to listen via the internet or can pay PPL royalties by way of a subscription so that people outside of the UK can continue listening. However, obviously some radio stations may in future try to pass the subscription charge on to overseas listeners coming in from non-UK servers. Expats on other forums have reported that whilst inputting a valid UK post code may work for a while it often gets permanently blocked after several weeks/months.
I can see both sides of this argument but it is one the record companies and PPL are likely to win.
The only moot point seems to be where an expat continues to pay a licence to the BBC every year in the UK on a UK property but cannot access BBC radio music stations whilst abroad.
If you can access a UK music station on the internet by inputting a valid UK postcode then enjoy it while you can because in a year or so's time you will almost certainly not able to do so unless a subscription is paid either by the listener or the radio station to compensate PPL.