BRITAX RÖMER KIDFIX SL BLACK SERIES, car seats 4 to 12 years, ISOFIX car seat, child from 15 to 36kg (Group 2/3), Storm Grey : Amazon.co.uk: Baby Products
DUALFIX - Installing the Seat - YouTube
Britax Romer Advansafix III SICT seat-belt mounting without ISO FIX (not recommended) - YouTube