Fluff, I would definitely have a friendly chat with them. Bring the damage to your fence to their attention first. It's the one tangible piece of evidence that is obvious.
Then you can mention your worries about further damage, this time to the house. Conifer roots, although wide-ranging, are quite shallow. It's very inlikely that they would grow under the foundations. The main problem is the amount of water they suck out of the ground. This could affect the stability of the ground the foundations stand on.
This would also affect anything that you try to grow in the area.
More immediate concern is the possibility of roots growing into drains. That's quite common.
If they're not willing to remove the trees, then one thing you could do is to have a trench dug, and create a root barrier on your side.