So I got it working finally.
I used the alexa-remote-control_plain.sh script from above mentioned link.
wget https://loetzimmer.de/patches/alexa_remote_control_plain.sh ./alexa_remote_control_plain.sh
Edited the script for the UK Alexa using below:
sudo nano ./alexa-remote-control_plain.sh
LANGUAGE=“en-UK”
AMAZON=‘amazon.co.uk’
ALEXA=‘alexa.amazon.co.uk
And your Amazon account email and password
Then I
sudo chmod +x ./alexa-remote-control_plain.sh
Then you should be able to run:
sudo ./alexa-remote-control_plain.sh -a
Which should return your echo devices
When you have found the name of your echo device, you can use the tts with below
sudo ./alexa-remote-control_plain.sh -d YOUR_ECHO_DEVICE_NAME -e speak:'I can speak'