I got a ticket parking on a single yellow line on a sunday but with no restriction sign anywhere near so this website really helped me get rid off the ticket.
http://www.donotpay.co.uk/signup.php
I really advise you to use it
Don't have to pay congestion charge if you're car is licenced with TfL as a private hire vehicle and you're on a booking.
No to bus/taxi lanes during their hours of operation.
I agree, they have very good templates customized for every type of PCN, when you use them you're making your appeal much more successful definitely recommended