Dear all, just wanted to give you an update on this small project that gave us such a big headache in case someone ends up in a similar situation. Putting steel on a half brick wall can be done. To cut the story short tony1851 saved our loft project as well as loads of money, time and most likely a timely and stressful case against the architect (although I am not done with him just yet). He managed to convince a very inflexible and autocratic SE from the LA BC that the project can work. Tony got to the bottom of what the exact concern with the wall was. It was loads of back and forth as the SE seemed to be moving the goalpost, but eventually with some alteration they agreed for us to continue with the work. I cannot thank Tony enough for his help. He is truly an expert in this field, he thinks outside the box and has wealth of experience and knowledge (plus his drawings are awesome ). The fact that he managed to convert and convince the SE who, it seems, made his mind up that this is not going to work, says it all.
Also, many thanks to all who contributed to this thread, I started to lose faith that we can have a habitable loft and your support and advice was invaluable.