I´ve only seen ATR ads i FI for captains (and a single one for f/o´s), so I can´t really agree with you, global pilot.
An ATR rating i Denmark with Danish Air Transport (DAT) costs around 170.000 DKK (£15.000) including tickets, hotels etc. I took that one and got a job with them right after. :o) Check out
www.ppjn.com for more info on DAT. -A very good course and for me it was of course worth the money.. :o)
The 737-rating, though, in my eyes, has a lot more potential, since there are a lot more well-pad jobs on the 737 around.
Good luck!