If you were to do a top half shot of someone talking on a white background like an apple guide video on the cheap what is the best way for a good result?
All it would be is one person from the waist up talking.

I suppose finding a good clean white wall and semi decent camera but the lighting is the key - any ideas or recommendations?

Large white sheet would be an obvious choice?  As for lighting?  Perhaps do it outdoors if you know somewhere very quiet; would probably choose a very overcast day, so no awkward lighting flare ups.  

Alternatively, there are many photography studios you can hire for a relatively budget cost.  They have lighting equipment already for your use and will have white screens etc.