Hi Darren,
Yes, they do bond to the original and should come with the original 'Elch' brand adhesive.
Trouble is, most of the spoiler (and body) kits are a few years old, and the glue has gone off.
I did a bit of research into getting new adhesive kits, but it was a non-starter and I was eventually recommended to use a good builders silicone adhesive.
Ideally, you need to roughen up the old spoiler and also drill 4 holes for the bolts to screw into, but I think they look very tacky and I planned to just use filler to hide any evidence of them, but it's personal choice.
The spoilers do come primed ready for painting, but they could do with a bit of work prior to painting (like filling in the rectangular part number stamp for starters, again with filler).
Mine is filled (the bolt holes are still there in case I changed my mind), primed and painted in Ebony Black Pearl, obviously to match Tank, but I daresay it's go with most colours, especially as the original is in satin black anyway!
Cheers,
Mike