Adult swimming classes (intermediate-ish)

Hi guys, I'm looking to do a swimming lesson to improve my front crawl. (I say improve, I really can't do the breathing at all, at all.) But in general I'm happy out in the water. I could tread water all day, can do the breast stroke or side stroke away fine. So I don't want to do a very beginnersy class.
But like I say, I'm unbelievably crap at the front crawl. So my worry is that if I go to an intermediate class I'll be behind but in a beginner's class I'll be bored. Has anyone done any classes anywhere? The options looking online seem to be the Maradyke, Bishopstown or a place in Blackrock called the Oakgrove. Any advice appreciated.
Ta.