I've got a Nipper 360 which I love. Turns on a sixpence, fits through most doorways (think it must be the same width as a lot of wheelchairs) and not too heavy. The only thing is it doesn't take car seats but I actually think that's not a bad thing - for DS1 we had an iCandy Cherry (which took a Maxi-Cosi car seat) and I think not needing to transfer him from car to buggy didn't do us any favours when it came to helping him get used to going back to sleep on his own. My DTs always look very comfy in their buggy a year on from getting it.

Another option would be the Britax B-Dual (I have one of these and highly recommend it).
I would say the Easywalker Sky Duo, but it says it's 75cm wide. Often you'll find that you can wriggle through a slightly smaller gap, but you may not want to try it if it's going to be expensive to return.
Or the Mima Kobi, but it's really expensive. The Bugaboo Donkey is 74cm wide but is also pretty expensive.

Oh and the TFK Twinner Twist Duo.

The main tandems that aren't too long for two car seats are the two iCandys, the BJCS and the B-Dual.
The only four side by sides I can think of that take two car seats and the main pushchair fits through your door are the Twinner Twist Duo, Donkey Mountain Buggy Duo and Duet. I believe the TTD car seats sit inside the frame possibly the Duo ones do too.
Is it not worth a flight over for your OH or someone else to pick a pushchair up for you?

I haven't used the Duo. It's very similar in a lot of ways to the Duet but bigger which means that it doesn't have the interlocking hoods, the handle height is higher, there's more room on the footplate etc. But t still has the incredibly annoying bunching up of fabric behind the childrens heads when you pull them up from a recline. The shop I last looked at the Duo had tucked the fabric behind so much to make it look neat that it took me a good 5 minutes to tug it free to try the recline out to see if the bunching up does happen (which it does). The fold is very large and flat. Positives over the TTD are the larger hoods, I suspect the handle goes up higher, it's slightly narrower, the basket is one large one, and it's a toggle (two handed) recline. Behind that the Twinner Twist is far superior. The quality of the TTD is good. The seats are thickly padded. The basket has a bar at the opening so slightly restricts say a large changing bag going in. The harnesses and shoulder pads are good. The hoods are a bit shallow - fine though - with a flick out visor, there's lots of storage pockets, the individual footrests both move up to make it longer and shorter but also lifts up to flat too. So fab for younger babies. The fold on the Duo is simpler. The TTD involves several steps but the end result is a far neater tri fold package with the fabric inside ie to kerp clean. It's relatively easy to lift too. I wouldn't want to be lifting the Duo every day - the Duet was a fair chunk! Both have nice carrycots. The TTD ones are roomy (so probably are the Duo ones) and I like the carrying handle in the top of the hood. I think it's got a mesh ventilation panel too. The TTD takes a variety of car seats. I believe the car seats on both sit inside the frame. The TTD ones I believe are staggered ie one above the other but on the Duo I believe they can / maybe have to be side by side at the top. the TTD has a foam covered handle. The Duo is a ridged rubber that personally I don't like. The TTD has a bouncy suspension. The TTD has a zip recline which is better than some I have tried but toggles are easier. But the fabric folds neatly and self velcros together when the child is sat up. For me, the TTD is far superior and offers greater comfort for the child.