Ahh, with you now.
You can break the seal with a small screwdriver or something of a similar shape. Slip it between the rubber and pipe, then move sideways or remove and re-insert further round.
Be carefull not to peirce the rubber, but they are pretty tough.
I managed to do mine without removing the pipe from the stat housing. Just remove the housing and hold it out of the way whilst you change the stat.