I've flown out of Luton several times wearing the exact same pair of sandals. Sometimes I've been made to take them off to be scanned, sometimes not. No rhyme or reason behind these so-called security measures.
None of it bothers me, it's only 10 minutes after all and no big deal. I always set the beeper off when I walk through and could never figure out why until someone told me recently it's my underwired bra!