Restore-SBFarm - How to make this work?

Hi, I've read through some docs on the restore-sbfarm cmdlet, which according to Microsoft does the same as new-sbfarm except with existing databases (full of data one would assume). Restore-SBFarm

I have tried to do this, but I keep running into an existing database error. If you try to use new-sbfarm against an existing set of databases you will get a 'database...is already configured' error. Fair enough, but I am getting this with the restore-sbfarm command.

Restore-SBFarm -GatewayDBConnectionString "Data Source=10.xx.xx.22;Initial Catalog=SbGatewayDatabase;User ID=servicebusfarm;Password=xxxx"
-SBFarmDBConnectionString "Data Source=10.xx.xx.22;Initial Catalog=SbManagementDB;User ID=servicebusfarm;Password=xxxx"
-FarmCertificateThumbprint '35B05CA7404141FD82142C0l9815456537' -RunAsAccount Administrator -CertificateAutoGenerationKey $CertKey

It then throws this:

Restore-SBFarm : Cannot validate argument on parameter
'SBFarmDBConnectionString'. The database (SbManagementDB) located at SQL
Server (10.xx.xx.22) is already configured.
At line:1 char:172
+ Restore-SBFarm -GatewayDBConnectionString "Data Source=10.xx.xx.22;Initial
Catal ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
    + CategoryInfo          : InvalidData: (:) [Restore-SBFarm], ParameterBind
   ingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.Servi
   ceBus.Commands.RestoreSBFarm

I have tried a different certkey password, which I believe is used to encrypt the contents? All of the other parameters should be OK.

Thanks