removal off a pulley on a jaguar v8 supercharged,?

hi
i need to change the timing chain tensioners on a v8 supercharged jaguar,i have started to strip the front of the engine,i am now as far as removing the crank shaft double pulley,does anybody no if they pull off or unscrew?,i have tried a pulley puller this keeps slipping off,also finding it hard to get one that fits perfect,has anybody got any idea's i can try or know anybody near tilbury essex that can assist,willing to pay,i just want to get my car back on the road.