I am just racking my brain here, but can’t understand why you cannot get normal TV, like BBC 1, ITV & C5 however I am unclear whether you mean that you turn off the V+ box or put it on standby.
I take it when you use your TV’s remote control that you are not getting a picture – check whether you have switched your TV to receive a digital or analog signal? (makes a difference)
Depending on how competent you are with the wiring on the back of your TV I would suggest that unplug your V+ and plug in the aerial to your Sony Trinitron and check that the TV is working, if it works OK then you will know that there is something up with your V+ box. If so call out the engineers. But only if you know how to put it all back again.
There is no reason why you should not receive terrestrial TV