Will I need to vary my lease now that the Renters’ Rights Act 2025 has been passed, as my lease requires me to sublet the property by way of an Assured Shorthold Tenancy Agreement

No, you will not need to vary your lease. The changes coming into force on 1st May 2026 from the Renters’ Rights Act 2025 will mean you can no longer create new Assured Shorthold Tenancy Agreements. Any existing Assured Shorthold Tenancy will automatically convert to an assured periodic tenancy.