Thanks to all of you guys who replied to my earlier query.
I had to fly away to Adelaide urgently after I made the post and just got home to Perth this evening. Sorry for the delay in acknowledging the responses.
The issue is now resolved to my satisfaction tonite. I used an X-Acto knife and went around the "groove" several times taking off bits of silastic/silicone with every cut and then used a bit of force to lift the lid and when that moved slightly I was able to insert a flat-bladed article in the gap made and finally pried the lid off without any damage whatsoever.
Cheers
Bill