That is a good one ladybarefeet. So sorry I neglected to mention that earlier. Thanks you kimluapi.
I was too focused (or NOT) on working in Edit Town.

When you place down a lot, say a 30x30 on an empty 30x30 and the terrain paint just doesn't quite match up. Unless its exact same lot, exact same lot it never seems to land properly. Mixed results getting around this.

So from what i can work out an empty lot placed in CAW (or edit town if you do it that way) is on a rotation. Hold down alt when your trying to place an empty lot in edit town and youll see what i mean about rotation. Its rotation determines how lots placed upon it will land.
A lot imported or built will have a "front" this controls which side of the lot sims will enter from. You can adjust that with the cheat.

So.. 2 things that may or may not work...
1)Experiment with different (90degree, no alt) rotations of the empty lot placement. Try to get terrain to line up. No so easy in edit town and more of a CAW thing.
2)I have in the past attempted to do as kimlupai suggests "set front of lot" cheat on the empty lot before placement but it occurs to me, you would not change the front of the empty lot as that will be determined by the building placed. Instead. Change the front of the building you wish to place>save to bin> place and see if it has any effect on the rotation it lands.

I have not tried the latter as it only just occurred to me.

I haven't played about too much with the cheat, so I don't know how effective it is. When I googled it, to make sure I had the right phrase I did see that some people had issues with the new front of lot not sticking so it may not be the perfect answer but I hope it helps at least a little.

Something that occurred to me, does the picture in the edit town library show the orientation of the lot to be placed? Is the front of the lot in the front of the picture? It would be useful if that were the case because then you could check which edge the new lot thinks is the front. Set that as the front edge in the empty lot. Then place the lot. So if for example the lot to be placed has been built with the 'front of lot' at the back of the building, you could set the back edge of the empty lot as the new front. Place the lot and in theory wouldn't need to rotate it. Then go into the lot in build/buy and correctly set the front of the lot. Of course that would only work if the pictures in the library show the front of the lot.

I'm sorry if that makes no sense or if I've just copied what Muzziah just said. It's been ridiculously hot here today and we're just not used to warm weather in the UK so my brain is fried.

I think the picture in the bin represents how the lot was orientated when placed before you rotate it. Or better said, ive placed houses which landed backwards, and then when i saved that lot to the bin the picture was also backwards. You rotate it and fix the terrain. Save it back to the bin, place it back into the world and again it doesnt line up. So no the portrait doesnt seem to have any effect on how the lot will be rotated when placed