Sorry for the late reply. Thank you so much for the detailed feedback, I appreciate it a lot and I intend to continue working on this and incorporate yours and the anonymous judges feedback.
They way I started creating the main structure was in individual pieces so good to know I started off on the right track at least! Thank you for also suggesting where to look for a glass shader as this was very tricky for me to work on. I will investigate this.
The anonymous judge suggested that to add more interest I could make the outside a different time of year, such as autumn and the inside is all green and full of life. Do you agree with this? Do you think this might also help with the contrast and perhaps make it not look like it's a greenhouse within a greenhouse?