Rather than continuing to hijack other posts I thought I had better create my own.
Last night I hooked up the 7" tft monitor I bought off ebay and arrived yesterday (car reversing camera set up), and all is working well. Picture is pretty good and it only needs a 12v supply which is an easy battery in the travel case.
I also managed to find drivers of an old USB easycap video device and got the picture up on my windows 10 PC as well.
I am still unsure about the housing penetration, so I am going to test a couple of varieties.
No 1, is using a cable gland, I will take the individual cores of the CAT 5, and mould them in marine epoxy in a cylindrical container to provide some solid for the gland to squeeze.
No 2, is using the open rov style flat channel between two plates full of expoxy.
No 3, buy a couple of the nice penetrators seen on here.
I am also looking at slip rings to transfer the signal of the cable reel that I can run out to any depth whilst still attached and watching the picture.