The definition of flight time for fixed wing aircraft is "The total time from the moment an aircraft first moves for the purpose of taking off until the moment it finally comes to rest at the end of the flight". If during the course of a flight, the aircraft carries out a touch-and-go or even lands, taxies around and takes off again, this does not represent the end of the flight. Only when the aircraft finally comes to rest is the flight complete.
To an extent, this leaves it open to the PIC to decide what he considers to the the final coming to rest and, therefore, how flight time is divided into log book entries but since, by definition, in a touch-and-go, the aircraft does not come to rest, it cannot be the end of the flight or the associated log book entry. As the OP points out, any number of discrete flights may be combined into a single log book entry provided that they all take place on the same day and consecutive flights are no more than 30 minutes apart.
Of course, if we are being really technical, whatever is in JAR-FCL 1.080 becomes entirely irrelevant in a couple of days time, but then AMC1 FCL.050 says exactly the same thing.