As a follow-up to this question MBP Mid 2009 thinks the lid is closed permanently I have identified (with a lot of help from google) where the closed lid reed switch is connected to the logic board, disconnected and insulated it.
The immediate side-effect of this was that my laptop now turns on every time without needing an external monitor or some voodoo where it would sometimes boot if I kept pressing the power button every time it went to sleep, this is a good thing.
A less positive side-effect is that I now have to manually put the laptop to sleep before I close the lid, not a huge problem if I'm honest. (Oh and the battery indicator lights no longer work, even less of a big deal)
My question is this, can anyone think of any other negative impact this may have on the machine over the long term? I'm considering just leaving the laptop as-is now.