On Sun, 13 Jun 2004 20:33:32 +0100, wrote:

It's a solid sheet about 20 x 12 and extremely securely fitted. I am
going to try a heat gun.

Hi,

Scoring it into strips with a knife or even a circular saw might help,
allowing each strip to be scraped or chiselled off at a time.

Another approach could be to freeze it with liquid CO2, dry ice or
possibly crushed ice and salt, and chip it off with a chisel in an SDS
drill.

cheers,
Pete.