The issue seems to be that the university is using the advent of ACA to justify this onerous requirement for a second insurance policy. And I would suggest that's the point you may be able to contest, with the aid of your Congressman.
...snip...

Let's hope they're thoroughly annoyed.
We'll see.

I am not looking to annoy them, particularly, but do not care if they are so. I DO want to get this problem fixed, for my daughter and all the other kids who will be in the same situation. Given that the year-long kids have to pay the NHS fee to the UK with their Tier 4 visas in addition to UC insurance... and that short-term students outside of Scotland in the UK have to pay a fee or pay for NHS, there's a lot of student money involved here. Maybe not a problem if mommy and daddy are paying the bills, and are wealthy. But for the rest, it's a substantial problem.
If there are 800 students going from UC to the UK, at about $2000 a full year they pay for UC insurance, UC stands to lose... a cash cow. Not a large one, but it's a chunk of change. I'd prefer to think that is NOT what they are doing this for, so I'm sure they want every penny they can get. My assumption is that most of these kids are on mommy and daddy's insurance anyway, so it's a moot point for them - as long as mommy and daddy's insurance covers them overseas. (Not all plans do, so if these kids are on one of the typical "Covered California" plans, they'll be in the same situation).
The U has no legal grounds to require insurance under the ACA; however, they
CAN require that students have insurance to be enrolled. (Still not sure they can require it over the summers, but that's not our fight here.) Many universities make that a requirement for enrollment. Since the guidance actually came, I believe, out of the Risk Management department, this is more about UC's Liability than any real concern for the students, I think.
As with most things related to the EAP program, they rolled this change out very badly, very very badly. The one comment I finally got from an EAP spokesperson at the Uni was "Well, we put the change up on our website and told the kids to be sure to read our website when they were selecting their programs." My daughter sat through two in-person group orientations where them not accepting NHS was not mentioned, she participated in a session where she was an invited guest and discussed her travel and time in Scotland with students who were going - in which she explained how the NHS and Travel Insurance worked since the person running the session did not know. At NO time was there ever a discussion of the issues we're having now. The "expense" budget worksheet they were given did not have a category on it for "insurance" - they just used last year's form (from when it was not required). So the extra 750-ish pounds was neither planned for nor is in her budget right now - she will have to borrow to cover the expense if they insist.
As I told the Uni EAP rep: who in their right mind would automatically assume that the NHS of a first world country would NOT be considered as equivalent to our rather pathetic Medicaid system (which is grounds for exclusion)? I got no reply - that happens a lot at this Uni, which is how I ended up involved in the first place. My daughter made several phone calls, left voicemail messages, and got no call-backs, (EAP and the insurance office people). Enter me. I made half a dozen phone calls and was bounced from office to office, and then back to the person who had denied the petition in the first place. I had to go to the head of the division to get someone to contact me to let us know who we COULD discuss this with rationally. It's moving now, so we'll see how it goes next week.