I've put a bit of thought into how I would sell a large amount and have decided it's best to wait for someone else to put up a significant bid wall and eat it quickly - that shouldn't affect the market too much. These large walls go up surprisingly often (manipulators I assume).

I would be really interested to hear other peoples opinions on the best way to do this too. Advice for genuine sellers / buyers who don't intend to day trade - simply buy or sell a large amount.