a little help with capacitive power supply values

[dhouston]

Just to throw a 'spanner in the works' , if I do eventually use a transformer based supply like the dimmer attachment, what would be the smallest footprint 220V to 9V/5V transformer I could use ?

One alternative would be to use a switchmode wall transformer that supplies regulated +5V. That way, it's external to your device and has minimal effect on the footprint.