Signal / No Signal Notification; Turn It Off??

I'm not sure if this is because of a recent update or I've just not noticed it before, but everytime my phone goes to no signal or finds a new signal I get a sound notification. So last night in my hotel where there is none to poor reception the phone was sending notifications all night; put it into flight mode to stop the stupidity!!

Had a look at all the settings but can't find anyway to turn this notification off or assign a silent notification to it. Any one got any ideas?

Z2 on EE, all stock.