To give an update on this:
I contacted
Manor Pet Housing regarding their guinea pig enclosure and asked if they could make a custom one for me and they said yes! So I ordered an enclosure with these measurements: 160cm wide by 80cm deep by 60cm tall.
It took 3 weeks to arrive and during that time my hamster chewed 2 holes on the cage, chewed the bars a lot, there was nothing I could do to stop her. Carboard she would instantly chew to pieces, putting things to cover the holes, she would take them out of the way, giving more toys, chews, etc, she wouldn't care for it. It was painful I'll tell you that but, alas, the cage arrived and I think she really liked it!
She explored the cage a lot, ran around, made burrows, you name it. She didn't even care for my treats, she was too busy haha. She still jumped upwards against the plexi glass all around the cage but I think that subsided as she got used to the new environment. I'm hoping to see her doing that less tonight.
I'm glad someone would be willing to make a custom enclosure, otherwise my second choice would have been a tank from Jungle Pets, even though that's more expensive than mine was for this size, I think.
This enclosure costed me £239.
From now on, I'll have fun decorating the inside. I'm thinking of making a rainforest theme. I'm so happy and relieved that this nightmare is over!