- Get a new sticky pad (don't bother with the Halfords sticky pads - they're rubbish) or get some of this 3M VHB Tape.
- It's a bit more awkward now the weather has gone cold, but you need to get the windscreen warm to touch and with no condensation/misting.
- Make sure there's no bits of the old tape left on the windscreen.
- Remove the remains of the old sticky pad from the camera mount.
- Clean your windscreen and the camera mount with Iso Propyl Alcohol (paint thinners may also work) to ensure there's no traces of grease or dust. Condensation, dust and grease are your three worst enemies when you're trying to stick something to the windscreen.
- Apply the new sticky pad (or VHB tape) to the camera mount first whilst not touching the contact area. Probably a good idea to this inside the house.
- Before sticking the camera mount to the windscreen give the windscreen area a final wipe over and dry off with a lint free cloth.
I used the 3M VHB tape when my camera dropped off, did the above and it hasn't moved since.