Recommendations for corner sofas?

Looking to change my sofa, ideally a corner chaise style kinda one, about the size of a 3 seater or close to an average 4 seater. Dark dark grey or black. Finding DFS and EZ living etc photos look great online but sitting on them in the shop they’re really really soft. Currently have recliners so not used to sitting cushions that move about and sink in. Ideally looking something firm. Any recommendations for stores or online? Been looking at Argos/habitat/b&q and just can’t seem to trust they’ll be any decent value for a £800 corner sofa.