Two questions following further research: -
1. Whether or not I really need to bother with C30 (Mains R.F. by pass) - do I require an X-type capacitor fitted across the mains tags between Live and Neutral?
2. The location of the switch S3 means that the mains is switched on the neutral - unless I am wrong this means that the wiring highlighted in
RED in the attached image will stay live when the switch is in the off position?