Are you a member of any cycling organisation like British Cycling, Cycling UK or the LCC? If so, they'll have a legal department who can help you with your claim.
Do you have home insurance that covers bike? You may be able to get them to counter claim.
If it's private land (ie Sainsbury's carpark rather than the street) I would write them a letter and ask for compensation to mend the bike then take them to small claims if they don't.
Jesus!
Are you a member of any cycling organisation like British Cycling, Cycling UK or the LCC? If so, they'll have a legal department who can help you with your claim.