Since posting to you I asked a question on the oil pulling support forum about amalgams, just to get a bit more info. Two members have already replied who have amalgams, have been OPing for six months, with only positive benefits.
Apparently its a bit of a grey area. I am therefore going to start again in the morning with sunflower oil (coz I have that in already), and, if I get any negative affects, will just stop it.