Hi there. Banks can be barstleshids can't they. When I was younger and doing my first eBay buys with paypal I accidentally incurred over £200 of bank charges. Fortunately, my mother handled it. I'm not sure it ended with the bank. I remember her getting pretty irate over the phone so I presume it was aimed at the bank. I think alot of whether the charges are dissmissed is based upon how serious/upset/offended you come across as.
If the bank doesn't budge you can go over their heads and make an appeal to the financial ombudsman. It's impartial and has the authority to do all sorts of finance-related stuff like dissmiss bank charges.
http://www.financial-ombudsman.org.uk/
I'm not sure if this will work for something so long ago but its definately worth a shot.
You pay Natwest £6 per month. Do you have one of those super duper accounts then? Otherwise your getting ripped off.
blue-cat