Security Code on Nokia 5210

I recently bought a new SIM card for my phone, but when I inserted it, it asked me for my security code. I have tried 12345 and various others, but I can't guess it. I called Carphone Warehouse, and they say that I'll have to pay ~£30 at a Nokia repair place. As this is about what it would cost to buy another of the same phone, I would really like to find a better way to do this.

Does anyone know how it could be done?

So far, I have tried opening up the phone (removed torx screws by grinding another screwdriver to the right shape :) ), and then doing various things to try and reset the memory, such as short circuiting the only battery looking thing I could see (not removable) and running an electric motor near it, but no change :(.

Thanks.

Can be done with an mbus data cable and NokTool

It is possible that he has tried the correct code, but after (i think its about 5) tries it will lock.

Yea, I never said permanently...
It will lock for half an hour...