If you enjoy soldering and builiding your own arrays with heatsinks, wiring, screw tapping, mounting, fine, but if not, more and more options are appearing on the market that are plug & play without breaking the bank. A net search using "High Power LED E27 base" will yield a multitude of info on LED options with conventional screw in type bases. Some of them will work straight off your household AC while others work with a 12VDC supply. Personally I like the MR16 two pin 12VDC form factor. You could arrange a bunch of these with little effort since they push in to the MR16 base very easily and it's not as large a connector as the conventional household E27 screw in base. I can see this being somewhat more water resistant as well, with a small rubber gasket over the base which you would then push the lamp pins through. You could also run them directly from a 12VDC source like a deep cycle battery, provided you have a reliable way of keeping the battery charge at the required level to run the number of lamps you plan to use. No drivers converting AC to DC to run your LEDs, which are after all DC devices. You could also add a potentiometer to dim the LEDs directly in line with the voltage source. The electronics geeks could make this dimming feature automatic, I'm sure. Below are just a few links showing what's available these days. A little more patience, these things will start dropping in price as LEDs slowly start replacing the CFLs which replaced the incandescents in our homes. If/when one of these burns out, yank it & replace it, simple.
If you're still keen on assembling the parts required to DYI a soldered array, knock yourselves out, but I'm waiting a little longer and will build either an E27 or MR16 based lighting system when the price & availability of this form factor drops in price a little more.
http://www.ledlightbulb.net/store/in...dex&cPath=4_31
http://www.dhgate.com/15w-high-power...b9aa25384.html
http://www.ledlightsworld.com/mr16-1...ight-p-99.html
I know this doesn't help solve the problems with your current LED job, but so many folks are getting caught up in this DIY LED array craze when there are easier options on the horizon.