You cannot add Sky Disney on its own. You have to add the entire Sky Movies package (11 channels). The cost will depend on your current package, but will be £20+ per month (plus another £7 a month if you want HD). The minimum subscription period is 30 days.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile