This is the gorgeous Vallauris Slate fabric by the Designer's Guild.
This particular piece measures 152cmL x 139cmW (please note that the equivalent of a small rectangle is missing at one end and this is reflected in the measurements. Please see picture).
Its official description is: "Softly tonal stripes in wonderfully peaceful tones are balanced beautifully against a 100% cotton ground. This stylish watercolour stripe is an ideal fabric for statement curtains, blinds, bedcovers, cushions and upholstery. Available in one tranquil colourway."
The Vallauris reference belongs to the Giardino Segreto collection: "An inspired collection of refined prints expressed in exquisite watercolour, paint and pencil shaded detail. In varying scales, this stunning collection is printed on linen and cotton in new combinations of sophisticated and timeless colourways. A perfect collection for elegant curtains, blinds, cushions, bedcovers and upholstery."