Currently at the committee-stage the 18th Edition will come into force at the end of 2018. The request for comments runs through until the end of August and is well worth signing up to the BSI to read the proposal and have a say if you see anything of note.
The most interesting change (for me) is section 8 - energy efficiency. All the changes to sections 4 onwards are better definitions and tighter specs for RCDs and earth leakage etc which are all very important but build on principles that are well established.
I'll post more as I get familiar with the draft, but here is the intro stolen from the IET site;
New section - energy efficiency
The worldwide need to reduce the consumption of energy means that we have to consider how electrical installations can provide the required level of service and safety for the lowest electrical consumption. The draft proposals enable a client to specify the level of energy efficiency measures applied to an electrical installation. Installations can also be awarded points for energy efficiency performance levels, for example, transformer efficiency. These points can be added together with points for efficiency measures to give an electrical installation an efficiency class, ranging from EIEC0 to EIEC4, depending on the number of points awarded. The new section will cover several energy efficient areas, such as electric vehicles, lighting, metering, cable losses, transformer losses, power-factor correction, and harmonics.