You can make a complaint directly to your installer by following their own complaints procedure however you cannot submit a complaint with FENSA.
FENSA can only get involved in matters where there is non compliance to building regulations on installations that have been completed and registered with us.
If your installation is not complete and you have exhausted the installers complaints process, you can escalate the matter directly to your local Trading Standards.
For advice about your consumer rights, see the Citizens Advice website.
Click here to find your Local Trading Standards Office