Is there a double faced heat sink for LEDs on MCPCB and...

[wheelema]

for the driver. It would seem to be a straight forward proposition though I don't know that it would be desirable. How do manufacturers handles this issue?

 

[luxrc]

there're MCPCBs which incorporate LEDs with buck or boost driver. some even have mode conrtol on it. so probably this will make your design simpler.
check links:
http://cutter.com.au/proddetail.php?prod=cut968
http://cutter.com.au/proddetail.php?prod=cut969&cat=39
http://www.lux-rc.com/view.php?p=content/magazine/new_LEDs