I found long lost LPCXpresso under pile of paper when tidying the desk - you just have to do it every now and then :). Below are the images of modification for the board to work with external debugger. When added jumper is closed you can use external debugger with standard 10pin Cortex connector. If your debugger uses VCC pin (1) for target supply detection you should shorten the R29. My board came without R29 placed.
Added jumper holds integrated debugger in reset.
I soldered the pinhead on both sides for robustness.