Final update - my dogs are a-barkinā tonight after walking back & forth between each park TWICE today!
I came here to report that Universal really did make things right by me though. I complained at guest services this morning & was given a $190 gift card to compensate the difference we paid for our 3, 3-day park hoppers. Absolutely amazing customer service here. We also got the private tour of Kingās Cross Station, although they tried hard to deny this request & were very pushy about wanting names etc of who had previously offered it. I had to go into semi-Karen mode to insist on it since we were offered this two days ago (but held out at that point for HE to hopefully reopen during our trip). Sad to not have gotten to ride HE, but all in all was really happy with these accommodations. Hope others have a similar experience (or, better yet, have HE up and running by your trips!)