No; bizarrely agents are not allowed (though they are for the FITs and the RO).
Chapter 2 of the government's RHI announcement says
Agents not allowed
We do not intend to allow agents, such as installers, suppliers or other third parties, to apply for support from the scheme on an applicant’s behalf.
We appreciate that agents were allowed under the Renewables Obligation (RO) and some have argued they should be allowed for the RHI, however we do not believe it is necessary. The original purpose of allowing agents under the RO was to help small-scale participants deal with some of the complexities of that scheme. The RO was primarily designed for large scale generators and small-scale generators often struggled to deal with trading small numbers of renewable obligation certificates (ROCs); the RHI scheme should be more straightforward and the more complex information at the smaller scale can be provided by the certified installer.
Enabling agents to apply on a organisation’s behalf would add complexity to the administrative arrangements and cost of the scheme.