Thanks for that, I've got on of their kits in my watchlist on ebay. How do you find it after doing it, were you happy with the results?
+1 on the Auber kit. I've had mine for years and it has been perfect.
The only problem I had with my Silvia/PID was that there is a known issue with the thread compound that Rancillio used to seal the pipe into the pump. It can dry out over time (years) and then start to leak. Mine did this and the leaking water then killed the relay unit that you screw onto the base at the back of the unit. Auber were able to send me a replacement and provided a very good deal on 48hr shipping from Canada (which I needed with Christmas fast approaching). I cleaned out the old thread compound and replaced it with PTFE tape.
On an unrelated matter (but whilstd fitting the PID), keep an eye out for rust on the Silvia. The black paint on the steel frame on mine was absolutely woeful (in the best Italian tradition) and I had quite a bit of rust after several years of use that was getting quite bad. I cleaned all the original paint off and repainted all the bottom section front and back with black Hammerite.
If I had my time again, I might be tempted to fit the PID internally rather than between the group head and the steam wand just because it will look far neater but it's certainly more work and means cutting a hole in the front of the machine.
[edit] and I owe the fact that I own a Silvia and Rocky grinder (plus lots of other gear!) and my passion for great coffee all to this thread which I started reading many years ago.