How to overwrite variables in a file with Bamboo variables

[Marinus Jansen van Vuuren]

I have a config file in my project

parameters:
  environment: development 
  redis.host: 127.0.0.1 
  database.credentials: 
    host: localhost 
    prefix: ${bamboo.agentId}
    mainDatabaseSuffix: main 
    mainDatabaseUsername: ${bamboo.agentId}_main
    password: password 
  database.host: localhost

As part of the build I copy this file, and would like to overwrite the values with bamboo parameters. How do I go about this?

I have tried 

sed 's/${bamboo.agentId}/${bamboo.agentId}/g' src/Resources/config/parameters.yml

also

sed 's/${bamboo.agentId}/$bamboo_agentId/g' src/Resources/config/parameters.yml

Also replacing the variable in the file with some placeholder

sed 's/BAMBOO_AGENTID/${bamboo.agentId}/g' src/Resources/config/parameters.yml

 Also heaps of other methods to escape etc but no success. Is there a way to replace all the variables in a file using bamboo rather than sed? If not, any tips on using sed for this?

Thanks in advance