I have resolved
Connect-AzAccount
Get-AzSubscription –SubscriptionName LH-CLoud-DR-Subscription | Select-AzSubscription
$vault = Get-AzRecoveryServicesVault -Name LHUSWest2RecoveryVault
Set-AzRecoveryServicesAsrVaultContext -Vault $vault
$BMS = Get-AzRecoveryServicesBackupManagementServer -Name "myserver.domain.com"
Unregister-AzRecoveryServicesBackupManagementServer -AzureRmBackupManagementServer $BMS
Plus going through UI and selecting the Vault and proceeding to go through the steps to delete the vault.