If one side is oxidized more than the other they would not be balanced with each other, so they are not truly in series then (and the hotter pickup may be losing signal into the other). When you select both you are not getting a signal at all, or just very low volume? Is there a massive audible difference between one over the other when selected individually?

That makes sense, as when I thought it was returning yesterday, it seemed as if the bridge pick up wouldn't kick in until I turned the volume over 1 and a half.
 
Thanks again btw fore pulling your knob out for me earlier (errr that doesn't sound quite right does it)

Scoot, the way to cure this is to bend the two middle connections ever so slightly outwards so that they apply more pressure to the outer switch half.
If you can make it so that the switch toggle feels very slightly loose in the middle position then you've got it about right.  If the toggle is firm in the middle position then it is applying pressure to the switch halves and breaking the signal.
 
I had to do this on a LP for exactly the same reason, no sound in middle position.

As for the hum.. that's something you're going to have to live with.  You can replace every lead, check every ground connection, ensure there are no ground loops,  but the RF generated by the dimmer switch in your neighbours bedroom will still be picked up by your guitar.
You may not hear it when playing clean, but as soon as you add gain it'll be right there.  It's that sort of background RF you can hear cutting in and out as you touch the strings or other metal parts on the guitar.
 
All the radio hams in the forum should be able to tell you about antenna theory, but put simply your strings (despite being 'grounded') are acting as antennas. When you touch them you add huge capacitance (yourself) which dumps any RF energy they're picking up to a "virtual" ground (that's you again) making the noise quieter.
 
 
As sharke suggested, walk around the room with the guitar to find the quietest spot, don't forget to try turning around as well...

Hum on a guitar...... something near and dear to my heart.
 
I have a classic Gibson SG with humbuckers.... the good ones... and if I get too close to a monitor it will hum. Distance, direction, angle, all affect the level.  The electronics and or wiring in the guitar should also be shielded.
 
A lot of the cheaper guitars.... the Epiphones, and the Fender MIM & MIC ...are all cheaper guitars. They have to use cheaper pickups and likely cut corners on shielding to sell at the price they do and still make a profit to stay in business. I haven't taken my Fender Modern apart to look..... but at $450 vs $1000 for a Fender Telecaster..... there has to be corners cut and cheaper parts used. I'm absolutely certain one of those corners is cheaper pickups.
 
On my Gibson, I have total silence...well no hum anyway with my amps and modelers. However, the Tele Modern is a whole different story. Depending on the pickup selection I use, I can get silent operation or hum that's pretty significant. And... the hum is also dependent on the gain settings I'm using. 
 
I have to choose which selector setting I use and when I use it. I often simply record the parts I want with the guitar and whatever noise is present..... and then use surgical envelopes in the track to cut the noise/hum to silence.

I'll give it a little time Karyn, see if it improves, if not I'll try your tip Karyn. In the mean time, maybe it's not such a bad thing, playing just either pickup, and getting to know the sound difference better, before I start blending.
 
It seems, upgrading the pickups are on every Epiphone players agenda from the reading I've done so far. I'm not shy of a soldering iron, but that for another day

I've got a Gibson Classic 57+ in the bridge and a 490R in the neck of my Epi 335; both sound sweet. I don't recall having any issues with hum while recording. As Karyn has mentioned though, manny things can be the cause...dimmer switch, wall outlet, computer monitor, etc.

Had a very similar problem with an Octa-Capture. Ran a wire from the Octa-Capture case ground to the grounded screw in the AC outlet plate. Problem solved.

Touching the case does make a difference, problem it, I'd have to run a wire from the case into the bathroom and to the electric showers earth. No way am I touching touching Vietnamese electrical system in this hotel. I've already experience an apartment fire when a neighbour's electricity meter went up in flames, taking the other 6 floors electrics and melting the plastic piped plumbing with it.