Thank you for your replies!
I noticed that this guinea pig had developed a minor fungal skin infection on Wednesday, and immediately informed my relatives that the guinea pig in question would require veterinary treatment - Imaverol and/or Itrafungol etc. . . -; that the environment/housing would have to be treated with either a dilute bleach solution, or appropriate disinfectant; and that the condition is highly contagious, and, therefore, handling should be kept to a minimum, and strict/good hygiene practices should be continued/implemented etc. . . !
However, despite booking an appointment with my veterinary practice, and offering to pay/treat the animal myself, I have received no support from my relatives, or the veterinarian!
However, the veterinarian wanted to treat for mites, and to take a hair/skin sample from the infected area to be sent for a culture, both of which I feel are unnecessary, and will delay recovery! Regardless, the veterinarian did not have the appropriate medication to treat for a fungal skin infection, and stated that they would not prescribed such treatment anyhow, as they are not convinced that the hair loss is due to fungus - Rather that the guinea pig has mites, or simply damaged itself!
However, as I have been made to feel like a complete imbecile, and told that I am being 'OTT', other than showing my relatives your replies, I really am not willing to invest anymore time, energy, or effort, or any of my finances, attempting to help this guinea pig!