I suspect you should do it within 3 days.

When you buy it could you email your PPU with the details explaining you can't register as it was brought in depatures. Then if you want to register it at the station as well do it when you get back.  I doubt any court would find you in breach for doing this. 

I have often emailed my PPU with new device information. She is happy to do this if I tell her in advance what I am planning to buy and agree to do it by email.

It might be worth talking to your PPU before you go to make sure you are covered. 

My SHPO notification only says I have to inform the police Visor team it doesn't detail how. There is no requirement in my SHPO to do it at the station.

I am in the throws of planning my Grand Farewell Tour to Europe in the Spring.

I have studied up on the notification requirements and feel confident I can comply.  However I have a theoretical question regarding new internet-enabled devices. 

If I were to, say, buy a new phone/tablet/laptop while abroad, then it seems I would be fine with making a notification within 2 days of returning to the UK.  But what about if I were to buy it from a shop in the airside departure lounge of e.g. Gatwick airport, then leave the country that day for a few weeks ? 

Common sense would suggest that the notification clock would only start the day I arrived back in the UK, but as we are all aware common sense is none too common in the criminal justice system - I would hate to be in breach for the sake of saving a few quid !

Thoughts ?