I read your post on the other site, did a little research and came up with this info...
I "believe" your machine uses hydraulic brake fluid, part # should be "JCB 4002/0503 Brake, fluid".
Please make sure this is correct, contact a dealer to make sure. You can google that part # also.
Engine oil would be 15/40 diesel oil. Your machine is similar to mine, mine is an 1995, does yours have the hoe on the back?
I use 32 weight hydraulic oil in the reservoir on the side of the machine.
My tranny uses 10 weight "special JCB oil", your best and safest way would be to contact a JCB dealer to confirm all of this, my brakes are different than yours and I have no reservoir for oil.