I found a great way to remove the old Clarion unit.
- Leave your car on a secluded country lane with the fascia in.
- When you return to your vehicle, a kind pikey will have efficiently removed the old unit for you, leaving a gaping hole and two plugs for ease of fitting the new stereo.
(Be sure to offset the £60 glass insurance excess against the cost of a decent auto-electrician first)
Edited to add: Just thought I'd mention that I now have an electrical fault that blows my lights and instruments if I play the new stereo. Worth having a think about before trying this method out