Thank you all for the suggestions so far.. Klutz unfortunately hubby is at work all day and I'm at home so would be vaping separately most of the day and vaping together in the evenings.
Right. Because what I would suggest is to consider a 'pass-through' eGo battery for home. This allows you to use them whilst they charge from a USB port on your computer or from a wall plug with a USB port (a few bob off amazon). So if they do need charging, your not left sod-out-of-luck.
That way you could probably get away with two batteries and just get two clearomizers. A good battery with 1000mah or there about should last a whole working day without issue; even for a pretty frequent vaper. Unless its consistent all day, but again could be charged in his car with a usb cig-lighter adapter or at a desk or whatever. The biggest issue is if it breaks, rather than battery life.
That should be enough to at least try, if it sounds like a reasonable option. If it works for you, get a spare battery or two, add some more clearomizers and buy a pack of heads for them.
One point I need to make, is that you should change juice flavours at least once a day or rotate in general. If you vape the same thing consistently you'll start to loose the ability to taste it! Hence, multiple clearomizers... for different flavours.
You could probably buy 2 pass-throughs (£30), 2 Kanger T3S (£10) or 2 Vision Ego V3 (£10) or one of each, and a selection of e-liquids to try. You could easily start from £40 from vapescape with that, and juice from anywhere. Bare in mind heads on clearomizers are disposable at a pack of them (and more clearomizers in general) are a good thing to have around; if going that route.
Providing others chime in with this idea!