The Effect of Digital Cognitive Behavioural Therapy for Insomnia on Physical Activity in Fibromyalgia

The goal of this clinical trial is to learn if a digital sleep therapy program (digital Cognitive Behavioural Therapy for Insomnia or dCBT-I) works to improve quality of life and movement in adults with fibromyalgia who also have trouble sleeping. The main questions it aims to answer are: * Does digital sleep therapy improve quality of life for people with fibromyalgia? * Does digital sleep therapy improve sleep quality? * Does better sleep help reduce fear of movement and increase physical activity, assessed in a virtual reality (VR) environment? Researchers will compare digital sleep therapy (called 'Sleepio') to standard care with sleep advice materials. Participants will: * Use the Sleepio program at home for 10 weeks (6 sessions, 20 minutes each) * Wear a sleep monitoring device at home in bed for several nights at the start and after 3 months * Wear an activity watch for 1 week to track movement at the start and after 3 months * Complete questionnaires about pain, sleep, mood, and daily activities at the start, 3 months, and 6 months * Visit the study centre twice for assessments that include: * Pain sensitivity testing * A virtual reality game that measures how they move and make decisions * Recording of simple exercises like marching and squats Participation in the study lasts about 6 months.