u/Impossible-Wave939

Hello. Has anyone put in an RSJ recently in london and can give me an idea of a cost. I'm thinking about purchasing a 1950s house. At the moment their are 2 rooms downstairs - a kitchen/diner and a sitting room. I would like to put in a RSJ to make it open plan. How much would this cost? Would I need an architect as well as a structural engineer? Thanks so much