I don't know about your area but, in my area photocell controlled Christmas light controllers were:
1) Crazy expensive
2) Cheap chinese crap made out of plastic.
Here's how to build a weather-proof controller in a solid metal box that should last you for years relatively cheaply.
Step 1: WHAT YOU NEED:
All parts are available from your hardware store.
1) Weather proof electrical box and cover. (~$7)
2) Photocell (~$10)
3) 3-Wire extension cord [ones with a ground pin] (~$12)
4) Two weather-proof cord strain reliefs (shown in picture) (~$1.50 each)
5) Three wire nuts.
1) Phillips and/or flat head screw driver (depending on the box you get)
2) Wire cutters
NOTE: I used a round electrical box so it will be stable and always point upward. You can use the square boxes but, be forewarned, they may tip over and point the photocell into the ground, rendering it useless.
Step 2: Install the Photo Cell
Install the photo cell into the box cover.
1) The photo cell will come with a gasket, USE IT!
2) Install the included blanks into the extra cover holes (if not already there).
Step 3: Assemble the Box.
1) Cut the extension cord in half and strip the wires.
2) Install the strain reliefs.
3) Install the extension cord through the strain reliefs and tighten (seal the reliefs)
4) Connect the ground wires (green) to the box (green screw). I used two crimp-on eyelets but, you don't have to if you strip the wires far enough back and twist them together securely.
Step 4: Wire It All Together.
Wire the photocell as shown...
Remember to run the wires THROUGH the box cover gasket so when it is assembled, the box will be water-proof.
Step 5: Assemble the Box.
Finally, just screw the box cover onto the box with the gasket in place.
...and you're done!
Plug it in and it will turn your Christmas lights on at night and off in the morning automatically!