Ruby,
1. It would certainly be logical.
2. As s20 is in effect just a special case of a local Act, of which there are many in E&W but not Scotland or NI, it will depend on the effect of the RRO on Local Acts; the original consultation document contemplated scrapping the fire requirements of them.
3. As in most local Acts, s20 itself is more or less enabling type requirements and contains no technical detail.
4. There is nothing scret about the requirements of the ACt itself. You can get the whole Act (London Building Acts (Amendment) Act 1939 from HMSO, or it is on a number of the technical online libraries to which you might have access. If you get really stuck, I can email it to you (but dont tell her majesty about the copyright breach).
5. As in all local Acts, the devil is in the interpretation, but in the case of s20, the interpretation is much better publicised than, say, the Leicestershire Act or the Hampshire Act. As Brian said, the info is in the LDSA Guide Number 1.
6. There is a tendency for some of the Boroughs to treat the s20 requriements as absolute, whereas others are more flexible. This makes prediction of the extent to which the will enforce some requirments (for hose reels for example).
7. the LDSA guide simply asks for a BS 5839 fire alarm system, but notes that for some premises such as hotels AFd is necessary.
8. Some s20 buidlings are high rise, in which case, for office buildings, phased evac can be used. If phased evac is used, LDSA have another guide, namely Guide Number 3.
