It sounds fitting, with GW back in the days having this nerdpunk ethos of joking anti-authority and not liking Thatcher, but when you examine it, you'll see that she was already out of office by the time Ghazkull was put into the game (starting out as an example warboss for the Goff's in the early 90´s Ork books). It is also not really close for it to be a good parody, either in the supposed likeness of the name, or the description of the character.
Source for this is having asked Andy Chambers, who wrote the part of that book when we had him as guest at some con's back in the 90's, and even before the widespread use of interwebs, there was an assumption that Ghazkulls name was a pun on Thatcher... Andy told us that it was pure coincidence, the name was generated from the actual random name tables. You would see parts of that table in the Ork Books of around turn of the 90's, and they might have been re-printed in later editions of the Ork list as well. Supposedly the original table was bigger, like the chaos daemon ones from about the same era, but got cut to half a page in its final version, due to space in the books.