Thanks guys, it is pretty sturdy. I started off by using those 1x2 hinge plates to make a round circle shape. The diameter is 12 studs, so you can attach a 12 stude plate acroos at any angle. Then each 1x2 section is built up using the combination of 3 round plates then a 1x1 brick with stud, then 3 round plates and then a 1x1 brick with stud etc, and keep going up like that. Obviously you have to alternate it so to the left and right of every 1x1 brick there is 3 round plates, hope you understand what I mean. Once you have got about 10 bricks high, its time to strengthen it, which is done by using 2x12 plates to criss-cross through out the tower. Just remember to use a 2x2 turntable plate to allow for crossing the 2x12 plates at every angle. Doing this pretty much means you can go as high as you want, strengthening it every so often and then attaching the tiles to the studs on the side. I will probably add this technique over at the guide, as its far easier than it sounds.
Oh, and yes, I picked up 30 of those viking pattern tiles from bricklink over Xmas and they are very handy for adding a bit of fancy engraving on buildings