I have a Dudley concealed cistern and it isn't flushing any more. Managed to remove the panel with the button and took a photo which can be found at https://sites.google.com/site/ishizbee/
No problem with the button unit itself and the tubing appears fine, so suspect it is the green unit with tis 03 on the front. If I can get a replacement part - unless there is something else I should be checking - is it reasonably easy to fit and/or does this require emptying and removing the cistern from the wall?