Motorcycle cops are now pretty rare in these parts- maybe Martin can confirm but I think its down to all the money they spend on speed cameras which are good at handing out tickets but are not good at stopping drivers / riders who have been drinking over the limit or on drugs.
When you do meet one while riding they will normally nod at you, and sometimes if you are sharing a lay bay or car park they wll come over for chat as many are bikers themselves out of uniform.
Both the speeding tickets I have been issued in the last 15 years have been from sneaky unmarked cars not bikes and after a few trouble fee years I got one from a camera last year when my V11 had a broken speedo- still my fault of course.
Be nice to them - they may catch the uninsured drugged up driver who may have knocked you off othewise.
Guy