I looked through some TV Times and old newspaper listings when this was shown on GMTV, and despite said TV listings mentioning guests on GMTV for that week there was no mention of this Heartbeat special nor any of the actors guesting on the show, which I find abit strange. Looking at some of the reviews I've read about Heartbeat from the TV guides it's not surprising really given the amount of namecalling. It seems to me that the critics and editors had a dislike for the show.
Found some great publicity stills of Heartbeat here on Pinterest: www.pinterest.co.uk/pin/18014467245738632/ Some stills from the earlier series too, alot of these you'd be unlucky to find on a general image search.