As Singingheart suggested, Novavax's nvx-2373 hasn't been approved as a homologous and heterologous booster yet in UK. Novavax applied for it on June 2 2022. Logically, the recommendation should be revised when the approval comes.
http://ir.novavax.com/Novavax-Files-in-the-United-Kingdom-for-Expanded-Conditional-Marketing-Author
ization-of-COVID-19-Vaccination-as-a-Booster-in-Adults-Aged-18-and-Over On the other hand, the exceptional circumstances applied to the Nuvaxovid just demonstrate how important the Nuvaxovid is to the JCVI as last resort to protect the public from any future unknown.