Tapering of Seroquel advice

I was put on 50mg Seroquel nearly 20years ago for panic disorder and general anxiety disorder with acute insomnia. I have tried several times to come off them but the insomnia is is wearing me down and end up going back on it just to sleep . I'm down to 12.5 mg at night just to sleep . Anyone out there who has successfully come off completely as there is a UK shortage and hard to maintain my dose plus causing irregular heart rhythm . Thank you