Option 1 (Concise):
> Embrace effortless style in our Plus Size Sleeveless Linen Lagenlook Maxi Dress.  This relaxed-fit, 100% linen dress features a round neck, drawstring side pockets, and flattering dip sides.  One size fits UK 12-18. Length: 48 inches, Pit to Pit: 22 inches.
Option 2 (More Descriptive):
> Indulge in luxurious comfort with our Plus Size Sleeveless Linen Lagenlook Maxi Dress. Crafted from 100% breathable linen, this stunning dress boasts a flattering round neckline and a relaxed, flowing silhouette.  Convenient drawstring side pockets and a stylish dip hem add extra flair.  Perfect for warm weather, this one-size-fits-most (UK 12-18) maxi dress measures 48 inches in length with a 22-inch pit-to-pit measurement.
Option 3 (Benefit-Oriented):
> Stay cool and chic all summer long in our Plus Size Sleeveless Linen Lagenlook Maxi Dress. This breezy, one-size-fits-most (UK 12-18) dress is made from 100% linen for ultimate comfort and breathability.  The flattering round neck, convenient side pockets, and stylish dip hem create a look that's both effortless and elegant.  Measurements: Length 48 inches, Pit to Pit 22 inches.  Perfect for everything from casual daytime wear to evening events.
Choose the option that best suits your brand voice and target audience.  You can also combine elements from different options to create the perfect description.