Loft conversion possible?

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Hi I have a general question about my terrace house, relating to a loft conversion. Having a large bay window at the front (2.4m) with a wooden lintel above, I have read on these forums that typically new joists in a loft conversion would be layed between the existing 2x4's supported on a flitch beam at the rear and front of the house, onto the side walls. On the left side of the house is a standard party wall all the way to the ground foundations. The other however, actually is suspended over the centre of the passage between my house and the other neighbour, by steel beams (see picture).



Not being an expert, I wondered if typically this is an issue when considering a loft conversion. These beams are obviously taking the load of the party wall and one end of the four purlins that support the slate roof (and the same for my neighbour's purlins). Is the extra load created by a loft conversion onto the side wall usually within the loadings of these beams, or are there usually other methods required? Apart from the arch in the centre supporting the shared chimney, there are seven of these that run between our houses supporting this wall. Obviously any loft conversion would be looked at by a specialist but it would be good if anyone had any expertise in this area so I can get clued up on the possibilities.

Paul