Bedroom being converted into dressing room, with tiles on floor and 6 wardrobes round the edge. Room is directly above rear end of double reception where the adjoining wall was removed a number of years ago and RSJ inserted. Perimeter of the dressing room sits on the perimeter of reception room / RSJ downstairs. Is there a potential problem with the weight of tiles / wardrobes?
You need an engineer to determine the load that the floor is designed to support and then you need to determine the live load you are imposing. You stated that the lower level underwent an alteration and a steel I Beam installed to support the floor joists. If you have the plans for that alteration they will likely specify the second floor structure and perhaps the design criteria. How large are these wardrobes? Are they larger and heavier than any other furniture that would normally be placed in that room?