Mk's quality has definitely taken a nose dive, the early sentrys were good and even had a sort of rubber grommet thing for top and bottom entries on the boards (on the placcy units), would have been ideal for this situation.
Speak of the devil, heres what the OP needs on ebay at a bargain price...
Are we all just splitting hairs about these IP ratings? If your that worried I would buy a metalclad unit and some blind grommets and cut NEAT holes in them
Right I'm gonna suggest something that I may get screamed at for by some on here, I don't recommend doing it but as you have no test equip. It may be the only way to test (ish) an RCD. I would remove rcd from board, connect a flex with plug top on one end into the top L and N terminals and plug...
One Neutral should come from the bottom of the Main switch into the first neutral bar, then from that neutral bar into the top of the RCD, then from the bottom of the RCD into the second neutral bar.
Well somethings got to give. IMO a properly done gland in a wall (hopefully a stud wall) is not a problem use a CW gland to take the strain off of the armouring . And use a pirana nut thingy.
I would point the OP to this thread with regards to Fuse size. http://www.electriciansforums.net/electrical-wiring-theories-electrical-regulations/76708-omission-overload-protection-fixed-loads-new-post.html
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc