Dyson DC04 Switch/Lead

After seeing the answer to this many times my lead has now failed. Dyson want 50 to send an engineer, yeah right! I can see the slot people talk about for removing but has anybody any info on what to use to get down the slot? I have tried a small jewellers driver and some jet cleaners but don't know if they are reaching the 'locking tab'. What length does the implement need to be and am I likely to have anything in my garage suitable?
Many ythanks
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