What's wrong with booleans?!
How did I do it:- Planes and extruding, cutting up cubes and placing them. Boring but it gets the job done.
How long:- One day,
I will work all day tomorrow at it (give or take a coffee break) and I will check back with you.
Jay:- Cheers for the textures, PM coming your.
Remember what Ninja say, only a fool refuses a weapon/textures