Welcome to the forum.
Stay away from whoever told you it was the "tailgate lift switch". It cold be a couple different things, but not that. Probably is the Remote Keyless Entry Module (RKE) which is located in the center of the dash. You didn't fill in your profile but I take it your from England. If you go to the United Kingdon PT Cruiser forum, they might be able to put you in touch with a trustworthy mechanic that will help you out. Here's the site:
UK Cruiser Club Website Dedicated to the Chrysler PT Cruiser.Events Forums and more.