Jordan Loughran, the actress playing the 14 year old child Leona, was actually 22 years old at the time of filming, older than Steven himself.
The filming location was done at RAF Bentwaters, now known as Bentwaters Parks, a former Royal Air Force station about 80 miles (130 km) northeast of London and 10 miles (16 km) east-northeast of Ipswich, near Woodbridge, Suffolk in England. It's no longer used by the RAF, and now includes a museum. The site is often used for TV and film, including Top Gear, The Grand Tour, and Fast And Furious 6.