Well I still get this left sided limb stuff, but the doctor said it seems to be transient (i.e it feels better, feels worse on different days) which is not how a life threatening symptom like a brain tumor would present. It would only get worse, not better.

An interesting thing I heard off my mother just now is that she was speaking to a friend of hers who has had recent anxiety problems following a cancer scare. She said that her left hand felt lame all the time, all weak and tingly. She also said that when her father lost his mother (he was about 30), he pretty much lost the use of his left limbs. Like he'd had a stroke or something. All due to anxiety as he made a full recovery on his own as he overcame his grief/shock.

So yes meg, I guess I can take comfort in the knowledge that its not that uncommon! (especially left sided for some reason).

EDIT : I'd still kill for a scientific explination though!