The OSSC1 used to be able to be used to apply to a chairman for leave to appeal but the version on the OSSCSC website now is set out so you can only use it to apply to the Commissioner and says "You must apply to the tribunal chairman for leave to appeal before you fill in this form"

Is there a new form for applying to the chairman?

in the "what's new" section of the cmmrs site @ http://www.osscsc.gov.uk/info/whatsnew_august.htm

it says -

"New procedures for applying for leave

Applications for leave to appeal to the chairman of an appeal tribunal do not need to be made on forms OSSC 1 or OSSC 2, or in any particular form. An ordinary letter, containing grounds of appeal, is sufficient. Form OSSC 1 should be used when renewing an application, or making an appeal, directly to the Commissioner. It is available on this site in two formats and can be completed on-screen (although it must not be sent in by e-mail)."