I imagine most companies might only deal with this once or perhaps twice ever, and if they do not keep very much personal data then automating it would not be very efficient use of their time. That's why in general I'd wait until you get such a request, ask your lawyer to explain it (will probably only cost a few hundred pounds), then decide what to do next.
Only very large companies (or companies that deal with a lot of personal data) will benefit from up-front automation.