LDC (existing) HMO C4 Application Rejected – What Next?

I have a small property in Leytonstone which has been let to 4 Sharers since 2007 and Walthamstow brought in a regulation last year to apply for a change in class HMO (C4). On the website, it mentioned that if it can be proven that this was in occupation by 4 sharers before 2014 then the LDC (Lawful Development Certificate) will be given.

I thought it was a given if I can provide proof – from 2015 it was let through an agency and before that directly by myself so provided Bank statements showing rent deposits from 4 sharers going back to 2007.

I’m now disappointed that it has not satisfied them, and they have turned me down. The agency has just started a new Tenancy contract for 4 sharers last month – what next?

Any advice will be greatly appreciated – appeals through specialists?

Many thanks

Samuel