Your correspondent Sutherland Lyall (AJ 7.9.00) ) seems to have had an atypical experience with the RIBA's Clients' Advisory Service website.
Having used it myself on a number of occasions, and found it to be an efficient way of finding practices, I was surprised to read of the difficulties he faced. The site does not require a visitor to use postcodes to find practices - that is just one useful option within the sophisticated search facility that of course allows for a name search as well. The error message he received when skipping through lists of architects is not a problem that I have encountered, although perhaps our browser is more compatible with the website than his.
Our view in this practice is that CAS provides a first-rate, low-cost service for registered practices, confirmed this week by yet another e-mail enquiry from a prospective client who evidently had had more success with the search facility than Lyall .
Tim Gough, Austin Winkley & Associates, London SE1