Hi Erika,
British Standards used to publish the document BS EN 60617-11 containing just the architectural electrical symbols costing £162
here. This was replaced by IEC 60617
here which has all 12 sections and costs around £330 per year!
In ArchiCAD itself there are a number UK spec symbols in the library already, but annoyingly named using just a code number which mean nothing to me! (and yes, they do look that bad in the folder preview!) These look different to the symbols used in our office, so I'm struggling to guess which is which.
The best I have found online is
http://www.cadcoaching.co.uk/electrical_comp.jpg
but this isn't a very comprehensive list. I'm coming to the conclusion that no-one seems to use exactly the same symbols! Even so, it would be nice to have a comprehensive list of the official ones.