We have just been through this process:
You need to use ACRO Criminal Records Office at www.acro.police.uk.
The charge is £55 per person for a Police Certificate (which is what is required) and they usually turn round an application within 10 days. There is a further charge of (I think) £15 for the certificate to be couriered to you.
The certificate then needs to be notarised (our solicitor charged £25 per person for several documents to be notarised) and then it needs to be approved via the Hague Apostille process (£30 per document).
Roberto - I believe that you are incorrect (which is rare). We did not have to provide any fingerprints taken in the UK, however, we have needed to attend the Foreigner's Office at our local Police Station in Spain, for an identity fingerprint to be taken (just the forefinger).
As per comments above, I strongly believe that you have been charged fraudulently for the 'Korean service', so I would advise contacting your credit card company asap.
As we've just successfully completed the whole NLV process, please feel to PM me if you have any further questions.