Yes there is a 'switch' - I hold Fn+F3 to turn wireless on, but it's already on when I turn the laptop on, so that isn't the issue.
I have a bit more information since last night - I've discovered that wireless WILL work IF I turn off the mode/router and turn it back on again - after the ten minutes it takes the modem/router lights to go back to green the laptop finds my network and connects to it - wonderful.
However, if I shut down or restart my laptop, the connection is lost, and the network disappears again, meaning I have to traipse downstairs, turn off the modem/router, turn it back on again, wait ten minutes for its lights to go green, and then the laptop will connect once again.
If I hibernate my laptop there's no problem - it remains connected.
So there's been an improvement - at least I know HOW to connect and stay connected, but it seems a bit strange that every time I shut down/restart the laptop, I have to turn off/on the modem/router to regain the network.