If anyone's interested, there's a (closed) Facebook group set up dedicated to problems people are having after the update - The Volkswagen diesel customer forum (emissions scandal) where 2-3 new members are joining on a daily basis complaining of bad running, dreadful mpg figures, limp mode, rattling engine and EGR failures! There's about 140 members at the moment and they're (we're) looking for more people who are having problems and brushed aside by VW. The more voices we have the stronger we all become - the admin have been contacting VW, watchdog etc and are not just sitting on their laurels.
Remember it's not compulsory to have the update done but at service time and perhaps your MOT they probably WILL install it without your permission!