Is there any evidence to suggest that having a general anaesthetic would have an adverse affect on a patient with mild multiple sclerosis ?

Yes: During surgery and general anesthesia a patient with ms can have a relapse of the disease. I always mention that during my preoperative evaluation. But, I have not seen that happening in 10 years. I put to sleep under general anesthesia at least 2-3 patients with ms a month without consequences. Depending on the severity, an anesthesiologist may ask for a neurological evaluation. Good luck.

No added issue: No problem with any of the commonly used anesthetics. However, I do NOT see you have listed any MS medication. If you have MS, you should be taking a disease modifying agent to prevent future problems. This is very critical, so please contact a neurologist and get started if this is a confirmed diagnosis.