Boot "open" light keeps flashing on dash

[j0nny]

Hi, whenever there is a small amount of vibration (i.e. car's going at over 30km/hr) the boot "open" light on the dash keeps flashing on and off as if the boot wasn't closed properly.
Someone said in passing (not in this forum) that it was a common problem...if so, has anyone else come across it? to me it sounds like it's a reed/pressure switch or something that may be faulty or not getting enough pressure on it. If so, does anyone know where it is?

Just bought me a '94 Legacy BD5 GT...mmmmm..looks good in black

Thanks in advance