scoobysnacks

I've got an MY98 WRX (42,000 miles )and it appears to be suffering from piston slap (knocking when cold, goes away when when hot). Now, can anyone tell me the definitive answer to this question? - How serious is piston slap? Will my engine explode, implode, melt, die etc. or will it just continue with no other simptoms other than the cold knocking noise. It's been doing it for at least 5000 miles, but probably longer without me really noticing until I read about it - I've only had the car since feb, 9000 miles ago). It's not burning any oil and I haven't needed to top up once, before or after my recent service. How worried should I be? How much to fix it? Is it worth it? etc. etc.
I've been told by a porsche mechanic that I shouldn't worry about it, just maybe take it more seriously in a few years (90,000 miles or so). Is he right or should I really sort it out straight away before something nasty happens? If so, can anyone recommend a contact name/number of someone who may be able to help, preferably in the London area.
Thanks for any help.

[This message has been edited by scoobysnacks (edited 11 October 2000).]