Don't do it...........
I hired my twin snap n go from Baby on the move, but seriously IMHO they are the biggest waste of space ever invented for the twin mum!!! They are about 10 feet long, and are stupid to put up and down, they are only a fraction smaller than a twin buggy (space wise) and you need to start turning the corner about five minutes before you need to cos they are so long..... Oh and did I mention tehy are loooooong........
Well that's my 2c. I imagine that for a single child parent they are worth their weight in gold, but I found mine to bee

and I have sent it back to where it belongs!!!!!
Well, anyway, if you didn't get where you can hire them from out of all that, Baby in the Move does a twin.
I do agree with mum2paris though regarding the prems and the position of their head, it is something that I was very aware of, and still am to this day!