Thank you for all the responses. Today I decided to take Vanda Exotic Purple out of its' pot, and I was not particularly surprised by the dreadful sight that met my eyes:
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I have trimmed away all the dead roots, which is approximately 90-95% of them, and placed the Vanda in a vase. I gave the plant a drink in the vase for 15 minutes; then poured the water out. I sprinkled a dusting of cinnamon over the roots as it is apparently good for treating fungal infections (I have used it before on one of my two Vanda Blue Magic plants - which ironically had a similar problem to this plant, but was switched - it declined in the vase, and is now faring alot better (in a pot) with good leaf and foliage growth; it has taken it over a year to recover - this is a different plant to the one that I have in spike at the moment).
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Fingers crossed that Vanda Exotic Purple will recover from its' operation!