Sounds like an old question!
You may find these useful:
ORS4 No 1125
ORS4 No 1124
The 1500 ft rule was part of Rule 5 which disappeared when the UK Rules of the Air were withdrawn following introduction of SERA
SERA.3105 Minimum heights
Except when necessary for take-off or landing, or except by permission from the competent authority, aircraft shall not be flown over the congested areas of cities, towns or settlements or over an open-air assembly of persons, unless at such a height as will permit, in the event of an emergency arising, a landing to be made without undue hazard to persons or property on the surface. The minimum heights for VFR flights shall be those specified in SERA.5005(f) and minimum levels for IFR flights shall be those specified in SERA.5015(b).