Shame I didn't come here earlier as I've already been messing with the fuel system in trying to pump the fuel out. I've still got a 6mm pipe connected to the fuel filter with the other end in a Jerrycan and I fear I may have let air into the system when I pulled the pipe apart (ringed). I was planning to suck out any air in the fuel filter with the bulb primer (when it arrives), fill the tank and then start it and if it runs, use up the old fuel, fill the tank again and when that is low, change the filter (hence the recommendation on which one to get).

I don't know if my diesel has been watered down, it probably hasn't. I guess I should wait and see if it fires up and runs before adding Diesel Cure, do you know if it can do more harm than good if the diesel doesn't need curing?