Carsick

Ok, a little story about my ride home from Preston last night.
I was on the M6, heading onto the M61 (had to stop at Chorley).
In the left lane on the sliproad an HGV was trundling along. I indicated and came off onto the second lane.
Suddenly, I became aware of the HGV's indicating right and starting to move into my lane.
I swung to the right, but couldn't leave my lane because somebody was almost beside me, luckily, the truck driver had seen me by now and stopped moving across; I nailed it and got past, the car that had been to my right got out of there sharpish as well, and the HGV came completely off the sliproad and continued on the M6.

From memory, there was a solid white line between me and the truck; I was doing 70 ish as I came off the motorway. I am sure that the truck wasn't indicating before I left the motorway, as well.

Am I to blame for my near squashing? Regardless I will be a little more carefull of this particular situation, but I'm interested in finding out the opinions on whether there was more I should reasonably have been doing.