Broad beans gone bonkers

I sowed a few early broad beans in pots about 2 weeks ago. I know it's a bit early, but with this warm weather I figured there was a good chance they'd be fine and I could get them out to the plot early too. Last weekend they'd come up nicely and so I've potted them on. During the week I was a way a few days for work and my family didn't water them and they'd all fallen over. However, the weird bit is that they're getting huge - well over 30-40 cm long mostly. They can't support themselves - it's almost like they're leggy seedlings, only huge broad bean versions.
As the weather's set fair I'm going to just plant them out on the plot and hope for the best. I'd like some advice though: how deep should I plant them? Should I bury part of the stalk and hope they can stand up themselves, or just plant out as normal and stake them?

cheers
Jerry

Thanks. I've been hardening them off the last couple of days. I can't believe how long they've got so quick. More like peas!!

It's February in Holland - we won't have strong light for at least another 3 months 
I'll put them up the plot and hope for the best.....

Mine have been out since November and are ony about that size. They are starting to flower though.

I sowed mine about two weeks ago too, I was wondering if I should start hardening them of or re pot them.
As you can see there all different heights.