As has been mentioned, in VMC, one can see the French coast long before reaching mid-Channel, so dead-reckoning isn't too difficult - not to say that VOR/DME/ADF/GPS/VDF shouldn't be used. Belt and braces - never let an instrument unused.
The schools in question might require an instructor, but they either want to make a fast buck
, or they need to remember that Louis Bleriot first crossed the Channel (with no navaids or ATC to help him) over a hundred years ago...
Cheers
