Pumpkin&Piglet wrote: I love the idea about flavouring the oil and re-bottling it to sell (or just give as cheap Christmas presents!) - do you need legal hygiene certifications for selling it?
Yes
For preparing & selling anything edible to the public the minimum you will need is to register your kitchen with your local Environmental Health Dept (they will come and inspect it) and hold a Food Hygiene Certificate. You are also best taking out some form of Public Liability Insurance too -- this will probably be a requirement of booking a stall on a Farmers Market or reputable Craft Fair
All in all, if you want to sell it -- you will have to pay out some money to do it legally
But you can just give it away as presents without any of this