hi guys, sorry I forgot to come back and reply, thank you for the comments. The reason I was considering the 'chemical' route, was it seemed like something different to try that I haven't before, and without risk of damage. The caliper is original, so I think its kind of cool to do my best to maintain it as opposed to replacing at the first sign of difficulty with a pattern part. I actually use my bike every day for commuting, so a broken ez out... order new part... re build... I could lose over a week, and the trains where I live have a habit of being out of service when I need them..
anyway judging by the comments I will hit it with heat and the EZ out or a torx bit and cross my fingers, as you say worst comes to worst I just order a new caliper half.
Ashley