Trying to remove my current stereo

I'm trying to remove my current Bose stereo (standard on my 10ae) and replace it with an aftermarket stereo from Lidl.
Problem - can't extract the old one - has 2 small holes on each side - have used a wire coat hanger pressed in both holes on both sides - it certaintly lossens it but it won't pull out - is there anything else i should be looking for ?
Also should i disconnect the battery or fuse beforehand ?
Cheers
Robin
Problem - can't extract the old one - has 2 small holes on each side - have used a wire coat hanger pressed in both holes on both sides - it certaintly lossens it but it won't pull out - is there anything else i should be looking for ?
Also should i disconnect the battery or fuse beforehand ?
Cheers
Robin