Not quite sure where to put this - sorry if should be somewhere else but can anyone tell me how to lengthen the straps on the Maclaren XT. The straps are now getting really tight (dd only 14 weeks) but I can't see how you lengthen them - there is some extra strap around the buckle but I can't get this to budge and I can't see any extra strap at top of the two top straps or the bottom of the bottom strap. Am I being really dense?