pigmeat in British English
a less common name for pork, ham1, bacon (sense 1)
The flesh, offal, etc., of a pig as food; pork.
1754 G. Colman & B. Thornton Connoisseur 25 Apr. (1756) I. 76 I was at one of their dinners, where I found a great variety of pig-meat was provided.
1784 P. Thicknesse Year's Journey through Paix Bâs 230 In short, (pig-meat excepted) he is a dealer in all things, and in all ways.
1817 Parl. Deb. 1st Ser. 743 It prevented the preservation of meat, and especially of pig meat.
1897 T. C. Allbutt et al. Syst. Med. II. 790 In most cases the infected food has been pig meat.
1918 Times 14 Jan. 4/3 Beef takes a long time to grow, while pig meat takes a comparatively short time.
1995 Daily Tel. 21 Nov. 6/1 A metal detector has been installed on the production line of one of Britain's main pigmeat processing plants.
Collins and OED give the spelling pigmeat; Merriam Webster says it's BE and calls it pig meat. It's not in the other dictionaries (Cambridge, Oxford Learners, Macmillan).
I don't think you should look too deeply for a distinction; the man on the street calls it all pork. The three dictionaries essentially say pigmeat is a synonym for pork, Collins describing pigmeat as 'less common'. I've never heard anyone call it pigmeat.
The AHDB link that you posted seems to be making fine distinctions (that would only be of interest to people in the pork trade) between different types of pork products. See the key to the chart: pork, bacon, ham, sausages and offal (pigmeat). That suggests pigmeat is being used to mean offal (but the opening paragraph talks about pigmeat and offal - ???).