The newly (1st April !) named West Mercia Safer Roads Partnership at
http://www.srpwestmercia.org.uk
has a useful Q&A section which includes:
Can I appeal against the notice?
Conditional offers of fixed penalty are a statutory procedure with no prescribed administrative system for appeals. What you are entitled to do is decline to accept the notice and request a hearing before a Court, when the evidence can be challenged and tested. You are free to write to the Central Ticket Office to express any mitigation or possible defences which you feel should be taken into account, but it is important to understand that payment is rarely excused, and only in the most exceptional circumstances.