I am quite sure that you may use your recorded calls as evidence in a harassment case - civil or criminal.
"For your own purposes" is likely to mean not for commercial use or for general publication.
I have no doubt that dislcosure to your legal advisors is perfectly permissible. I think that it is inconceivable that a court would refuse to hear evidence of criminal or civil wrongdoings by a DCA or other commerical organisation simply because the company had not been warned that their harassment would be recorded.
We already have some sound files from DCA telephone calls. I can confirm to you that solicitors who have already heard the recordings have raised absolutely no objection whatsoever to the way in which they have been obtained.
We have also already informed one financial institution that we have recorded evidence against them and they have not even raised the issue of prior consent. I cannot believe that they would dare.
Even if there is a query over the recording of phone calls, I believe that the following arguments can be applied:-
Self Defence - reasonable force or other proportionate measures to protect the person or property.
Mutuality - companies will be recording their calls to you. You benefit from implied reciprocal consent.
If you are at all concerned about recording your calls, (and you shouldn't be) then simply send a letter to the regiestered office of the company in question and put them on notice that you will be recording any calls they make to you or that you make to them.
Keep a copy of the letter. This formal notice will be more than adequate to make sure that any legal obligations to give prior warning will have been satisfied.
There is no need for you to warn each new caller in respect of each new telephone call.
Finally, a plug: Do have look at the Truecall call recorder which has been reviewed by Steve4064.
TrueCall digital telephone recorder
It is a little pricey but it is an astonishing machine and will help you deal with all of your unwanted calls completely.
We would suggest that for the beginning, you do not screen out calls. Instead, you should set about merely recording calls and gathering evidence.
Don't forget our offer to you:-
If you supply us with recordings of calls which demonstrate harassement, we will have the recordings transcribed for you free of charge.
Recording Phone calls 
