Thanks TGM and sorry it's taken me so long to reply.

Our current house is 133sqm and I reckon we need about 200-230sqm.

Now I think I have come up with a GENIUS solution. A while ago I was looking at module houses - you can get some really stylish ones for $2K per square metre. Now architecturally, they're fairly boxy and simple so while I thought one would be fine as a granny flat sort of set up at the back of our current block, I didn't think I'd want the whole house in that style for our new house.

But, having thought about it again, I think there is a compromise to be reached. We could have an architecturally interesting building for the living/dining/kitchen/2nd living/office and connect it through a glassed-in walkway to the bedrooms in a different section. And we could have a module for the bedrooms because I don't mind so much if they're simpler and a bit boxy. So I reckon each section would be 100sqm each.

The house/block we're looking at already has a garage so we don't need to worry about that. It also has a 2br house on it so I'm also thinking that once the module gets installed, we could use the bedrooms in that and then use the existing house as our living areas until our new house gets built. We'd then keep the existing house and use it for guests and possibly rent it out as a weekender. The block is 5 acres so it's not like we'd be cramped!

Anyhow, that is my latest plan though we haven't been able to see the block yet!!!