97 audi a3 8l heater matrix removal

hi guys new on here but i'm having to replace the heater matrix on my a3 tdi 110 as it's leaving a puddle of water in my foot well and condensation/ misting up.
i have removed the dashboard and now trying to figure out how to remove the heater assembly but can not figure it out or see a way of doing so.

could anyone shed some light on how to remove it?

thanks in advance Steve.