Much better since the advice.
I now check behind when I'm about 200m from the pinch and try and eyeball the driver. Then when about 100m from the pinch I check behind again and do a sort of half turn right signal, but more of a "thankyou" wave and pull into the middle, or near the middle.
Then I get back over to the left as soon as I can after the pinch, and give the driver a proper thankyou wave.
Last couple of days I've had no close passes, no aggro. One driver looked like he was going to try and squeeze through, but thought better of it at my second look behind. He didn't seem bothered though.
Thanks for the tips everyone.