HB
Check the DIY retailers - there might be a solvent available for bathroom flexible sealant - that'll probably do the job.
If not, maybe try cellulose thinners - it won't dissolve it but it will help loosen the bond with the ali so you can winkle it out more easily.
You might also to try a hot air stripping gun - BUT NOT WITH THE THINNERS!!!
DON'T be tempted to muck around with strong acids or alkali/caustics - you'll ruin your nice new surface!!