The two auxilliary electric fans on my recently acquired 1997 Discovery V8 weren't working either until I replaced the motors (with Nippon Denso parts for the equivalent of a little less the USD100), didn't notice because the main mechanical fan was doing it's job (temperature never exceeded mid-point). Nevertheless, replaced them for insurance (automatically turn on with the air conditioner or presumably if the engine temperature exceeded a certain level). Now the temperature gauge seems to hover a bit below mid-point most of the time. Would suggest you do the same if you haven't already. They say aluminum engine blocks, heads & gaskets, as Discovery 1's have, don't do too well with heat build-up.
mine weren't working and i didn't have the cash to replace them at the time so i removed them, if there not in they increase the airflow through the radiator, if they are in and not working then there just blocking precious air from the radiator. my advice get a thing of Prestone radiator flush, empty all your old fluid and refill your radiator with water and run the engine till it heats up so its circulated, drain the water, and repeat a few times then repeat the process with the prestone radiator flush. finally refill your radiator with coolant and add 2 bottles of lucas super coolant. mine runs cooler and more consistent than ever before. my rover mechanic who is a veteran mechanic and has been working on land rovers since forever said i would need to replace my radiator before i did this then after i showed him and he couldn't believe the difference.