As you may have seen
I too have a bunch of Forge World scenery.
I had a similar "problem" with one of the bars of the Well, they were bent and didn't fit. Remembering the info from the website I put the piece under warm/hot water. Not too hot so that I would burn my hand but pretty warm nonetheless. Straight out the water tap. I was surprised at how easily the resin can be shaped. I'd use warm water since it worked well and you have to wash the piece anyways. If you use a hair dryer I suggest being very careful. As I said, I was surprised at how easily it could be formed after the warm water so make sure you don't apply too much heat - I can imagine it melting!
So bottom line, I'd use warm to hot water and only resort to a dryer if that is not sufficient. Good luck! Tell us how it works!