I'm feeling a lot happier since speaking with the Surgeon over the phone about my cast and removing it.
The cast (if you could call it that) was a bit Heath Robinson in its construction and felt very loose on my arm leaving me feeling quite vulnerable, so after chatting with the Surgeon about the wrist support I still have from when I shattered my wrist 10 years ago, he agreed I could remove the cast and use the wrist support instead, especially as it has a metal insert the full length of it for protection. This is far more comfortable and feels a whole lot more secure.