Hi all. I have the silver cross wayfarer travel system. I have washed all of the covers that seem to come off in my machine on a hand wash cycle and they've done out great however for the seat I can't seem to get the covers away from the supporting material inside? Could anyone advise if this is doable and if not how they went about washing them please? Image of the seat to show what I'm talking about - the covers come away from the chassis and frame but not the internal support. Thanks!