Hi,
The carrera TDF is not an expensive bike, and you bought some 28mm tubes ....
For winter for £12 each delivered you could do a lot worse than a 28mm pair of these :
http://www.chainreactioncycles.com/michelin-city-road-tyre/rp-prod26232
Go for the version with the reflective stripe at no extra cost.
I've got the 32mm on the front of my bike and FWIW one of these on the back.:
http://www.chainreactioncycles.com/schwalbe-speed-cruiser-tyre/rp-prod68177
Note the City looks like the second photo, not the awful first photo.
At near half price you can't go too wrong with a tough very long lasting
tyre with puncture protection that rolls very well, but its not a lightweight.
I've no idea what the stock Kenda 23mm tyres are like, you could use
them in summer. Note that if you run the 23mm's about 100 psi you
should run 28mm's about 70 psi, the back harder than the front.
rgds, sreten.