Kwik Sew 3644 is a good basic pattern for a dressing gown in two lengths, with or without piping and/or contrasting fabric. The fabric required for making view A (the longest version) without contrast fabric is not stated, which is annoying. I cut my garment out of 2.3 metres of fabric 150 centimetres wide but only because I cut some pieces upside down or sideways. Ideally, I would have liked 3 metres x 150 cm.
My fabric is Liberty of London's poplin, a design called Carline, bought on eBay. Matching pyjama pants can be expected soon.