@excitednerves you won't regret the mountain buggy, it is fantastic from birth to large toddler, and my duet is the same width as my swift, plus the parts are so easy to access either new or second hand. I will probably replace all my wheels with the hard ones from their website, though you only usually get like one puncture a year or something. And standard inner tubes from bike shops or Amazon ect will fit as the wheels are either 10 inch or twelve.
I am seriously Mr myagi on mountain buggies so ask anything you need.
(Except if a pre 2015 swift carrycot will fit on a post 2018 duet 😆🤯)