I don't think you can disconnect it.....or at least disconnect the pump, its integral to the power brakes whether the ABS is enabled or not.
Of course, I'm assuming that its a pump/accumulator type system, the pump basically pumps up the pressure in the accumulator, that is where your power brakes come from, as the pressure in the accumulator drops, the pump comes back on the charge it back up. I had a Jag XJS that had the same type system, sometimes the accumulator ball can go bad and causes the pump to run often, also the pressure switches can go bad, or the pump itself. On my Jag the brake fluid was old/contaminated and when it got really hot here in Dallas combined with the really hot temps under the hood in that car, the fluid boiled or something and the pump just ran and ran and I had no brakes at all....once it cooled off, all was fine, I changed the fluid and no problems after that. On the Jag, the pump was acutally an AC/Delco part, while the off the shelf replacements from GM were not cheap either, you could find them on certain model GM cars in the scrapyard. Seems like I saw a pic of the Rover pump and it looked similar, but I might be mistaken.
Fortunately, my 1992 RRC was one of the few without ABS, part of the reason I bought it.
Of course, I could be totally confused and this is all wrong...LOL
*UPDATE*
Went to Rangerovers.net and looked up the info, it is a pump/accumulator type system, so you are stuck with the pump until you replace it with a vacuum type booster from an older RRC...not sure what your other options are.
http://rangerovers.net/repairdetails/abs.html
