Following a posting and subsequent clarification on the APRS UK Yahoo Group I have discovered that in order to legally operate an APRS digipeater or Internet Gateway it is necessary to apply for a Notice of Variation (NoV) to my license that must include the nomination of at least three people who can close down the station within 30 minutes, even if the station will only be operated when I myself am present.
The reason for needing an NoV is because all authorization to transmit third party traffic (i.e. traffic not from you, nor for you) was removed from the new Lifetime License that was introduced in 2004. I don't actually have any problem with needing an NoV, though I'm sure I am not the only person who used packet radio back in the '80s without any special dispensation and didn't realise that this was no longer possible. However, the requirement for the NoV application to nominate three closedown operators even if the gateway or digipeater will only be operated when the licensee is present is simply ludicrous, as well as being a major obstacle for anyone who does not have three people who can meet that requirement. If the rules are silly, I won't play the game.
As I understand it, it is legal to transmit position reports on RF (because they are from you), it is legal to transmit APRS messages (because they are from you) and it is legal to run a receive-only Internet Gateway (because you are not retransmitting what you receive.) But digipeating or transmitting packets received from the Internet for other stations heard by you is carrying third party traffic and therefore illegal without an NoV. I think many people such as myself who are not dedicated APRS operators but see it as just another mode to use from time to time will take the easier option of operating without an NoV even though in the opinion of Rob Compton M0ZPU receive-only gateways "cause problems to the network in terms of it's capability to carry messaging ... by causing "dead-ends" to intelligent routing (where software utilises the reverse route for a message)."
It's hardly surprising that the RF APRS network in the UK is so poor compared to the USA and other parts of the world.