there was a tiny little lip around the bottom once I'd removed all the crap inside. Pair of needle nose/circlip pliers got it out quick marchWhen you clear the sh1te out if you work a small hook under the front of the base panel and pull it upwards all will be revealed,I've Just done it on mine to remind myself how to remove it.this is what I used.work the tip in,turn 90 degrees and pull up.