My first real attempt to build a temperature sensor that would be suitable to mount on the wall was not a success. The telephone coupler from a diy store was just to fiddly to fit the bits inside.
However, I still liked the idea so I tried these Junction Boxes from ScrewFix. I paid 4 pounds for five on the off chance they might be okay.
Well, they were better than okay. They were perfect. I cut a couple of small notches in the metal contacts running across the box and bent the legs of the DS19S20 sensors under and it worked - no soldering needed.
To finish them off I just drilled a couple of small holes in the cover. (Hint: drill from the inside out - it leaves a better finish.)