Thanks buddy, yeah that looks like it would cover the parts needed. I've now had a reply from Sea & Sea Head Office and they have quoted me the part numbers to order. If anybody in the future needs these o-rings I have attached a picture of the parts I mean and here are the part numbers as quoted by Sea & Sea (although I haven't ordered them yet so I can't guarantee this is 100% accurate.
"O-Rings inside of View Finder in the back of the housing where the part is see-through
MDX-RX100 Mark 2"
Black : X-10645 S-80
Blue : X-11082 S-60
I'll let you know if they fit once I get them!