Upvote:3
No. Since it is only a single entry visa, you cannot re-enter the Schengen region once you leave it. Going to the UK would mean leaving Schengen.
Upvote:3
No. You can visit France and Italy, which are also within the Schengen zone. There is generally no border control between those countries, and if there is a spot check, you will pass through with no problem.
The UK is not in Schengen, and when you leave the continent to go there, your single-entry visa will be canceled and you will be unable to get back in.