Here's the approved phraseology straight out of MATS Pt1:
Turn left/right heading (three digits), report established on the localiser.
Closing the localiser from the left/right; report established.
Descend on the ILS, QFE (pressure) millibars.
Descend on the ILS, QNH (pressure) millibars, elevation (number) feet.
When established on the localiser, descend on the ILS, QFE (pressure)
millibars/QNH (pressure) millibars, elevation (number) feet.
Note the complete absence of the word cleared.
If you were "CLEARED to descend on the ILS" then the controller was being slightly careless -- it's an instruction not a clearance. If you were "CLEARED ILS approach" then it was either a procedural approach or the controller was using phraseology that is not usual in the UK (though standard everywhere else on the planet). More likely, I suspect your recollection may have embellished the phrase to add "cleared" -- UK ATCOs are in my experience very good at adhering to MATS.