VOA Council Tax Assessment for individual bedsits

Tenancy Types and Management

The VOA (Valuation Office Agency) want to reassess my 6 bed HMO for council tax purposes. The rooms are currently rented out individually, bills included, and all have en-suite or exclusive bathrooms and are fitted with a sink and fridge but no cooking facilities. A communal kitchen is provided. The VOA have stated that they may decide to assess each room separately for Band A council tax making the property much less affordable for tenants. Council tax would become individual tenants responsibiity. If the tenants, who have become friends, terminate their current individual AST tenancy agreements and agree to a joint tenancy for the entire property would this oblige the VOA to assess the property as an HMO for council tax purposes rather than as 6 separate units or is the type of AST used irrelevant?