I would go to your local hardware shop. Online sources are all expensive for that. Think my brother also paid something like £6 for a few litres.
That made me think though... does the stuff have a shelf life?
http://www.fireflyfuel.com/blog/what-is-the-shelf-life-of-paraffin-oil do the lid up and it'll last forever.
Paraffin is awesome stuff, ive also used unleaded petrol before to clean chains. Both work very well
That's a myth,a guy tested it on o rings,he soaked them in petrol for a week and they didn't swell
It simply wouldn't be on the chain long enough to do any damage