renamed databases causing issues

my hosting company upgraded their server environment and 'helpfully' migrated all data but in the process renamed the database holding perch data, and put in different username password etc.

I have all that new info now in my 'config' file but apparently still no joy...

in this scenario is a fresh install of perch required via 'setup'?

or is there a solution to reconnect the website with the original data and resources???