N-Reg Confusion

[Islander2]

From the AIP:

"When operating on a Special VFR clearance, the pilot must comply with ATC instructions and remain at all times in flight conditions which enable him to determine his flight path and to keep clear of obstacles. Therefore, it is implicit in all Special VFR clearances that the aircraft remains clear of cloud and in sight of the surface. It may be necessary for ATC purposes to impose a height limitation on a Special VFR clearance which will require the pilot to fly either at or not above a specific level."

From the Rules of the Air:

(k) ‘special VFR flight’ means a flight—
(i) made at any time in a control zone which is Class A airspace or made in any other
control zone in either Instrument Meteorological Conditions or at night;
(ii) in respect of which the appropriate air traffic control unit has given permission for
the flight to be made in accordance with special instructions given by that unit
instead of in accordance with the Instrument Flight Rules; and
(iii) in the course of which the aircraft complies with any instructions given by that unit
and the aircraft remains clear of cloud and with the surface in sight;

Edited to add the actual legislation from the Rules of the Air. Boy, I've got too much time on my hands today!