In this situation you can explain clearly in the ‘Reasons for appeal’ section of the SEND 35 appeal form why the OT report is relevant to your appeal, for example because it supports the changes you are requesting to Sections B and F of the EHC plan, and that (if applicable) you are unable to obtain any other OT report at this stage. 

Once your appeal has been registered, you can then use the SEND 7 ‘Request for Change’ form process explained here to request permission from the SEND Tribunal to admit the OT report in full, and if this is not acceptable, to admit those pages of the OT report which support the changes you are requesting to Sections B and F of the EHC plan.