S ome of my most traumatising experiences have come hosting children’s parties: the Wardrobe Ensemble’s new show should come with a trigger warning. This devised play pitches us deep into the parcel-passing, E-number-addled tantrumscape of a weekend shepherding one’s five-year-old to three (three!) tots’ birthday bashes. Such is the burden borne by 34-year-old Xander, recently – and reluctantly – back in Bristol after a temporary escape to London, obliged to reconnect with old friends and painful memories across 48 primary-coloured hours of musical statues, puppet shows and small talk with people whose kids happen to know yours. For much of Party Season’s 95-minute span, we’re in the territory of the sitcom Motherland , a broad comedy of manners about competitive parenting, sleeplessness and ideal-home envy.…