I know it's not something you thought you'd see in this forum :)

But watching ebay there are a few for sale under £30.

What's the difference between:
120S
120N
120FN
120CFN
120GFN

Like, what's with a GLASS lens in a Holga?
Does that raise the quality (hah!) to the level of a Kodak Brownie?

Why one with a flash?
Surely I can make my Canon 580EX work :)

Advice please ... maybe I'll try F1 photography with a Holga.
Driver portraits perhaps :D

To answer your question...
I think this will probably be moved to one of the other forums, but here goes...
The "S" model is the original version of the Holga and prefered one for that matter
All others are the newer verions. The "F" versions come with a flash. The "CFN" has a flash, but it also has spinning color wheel that you can choose from red, yellow, blue, standard white or a combination thereof.
The major difference between the S and the N versions are that the N models have a bulb setting and a tripod socket.
I'd go for the one withut the flash and use whatever flash you use with your dslr.
HOWEVER...
I would recommend you buy one from one place and one place only..
Check out.. www.holgamods.com
Don't buy a WOCA, HOLGA is it!
So Go For It! You'll love it!
Make sure you post some stuff!
Good Luck!
Brian
Holga Rocks!