Odds would likely be better at UBC/McGill.
LSE and Imperial tend to admit student just a bit below Oxbridge level. Keep in mind that British students are only allowed to apply to 5 universities so the acceptance rates can’t be understood like in the US, where most top students apply to 10+.
LSE and Imperial may be reachable reaches but a student with these as reaches and 5*5s&3.7+ could get into excellent US universities too - most state flagships except for a handful, for instance.
The ECs you mention would be very useful to a US college application list.
Hockey would be appreciated at some top colleges for Economics - Amherst, Bowdoin, Colby, Connecticut College… If he can get coach support&he passes the academic pre read in June of a junior year, it’d be a major hook.
There are over 2,500 4-year colleges and the top 10% are excellent. You can buy a Princeton Review’s Best Colleges to get ideas.
In the UK, look into St Andrews, Durham, Warwick, U Edinburgh, for universities in a more manageable environment.
Scottish universities are 4 years and have a bit more onboarding. St Andrews fosters close relationships and Edinburgh, despite being a capital, is more manageable than London.
Durham, Warwick, York, and Queen’s Belfast are Collegiate Universities - the broader institution has its own colleges within, helping in socializing and networking.
London universities expect a lot of familiarity with living on your own in a big city. Students are spread all over the city and typically must know how to shop and cook for themselves (though some “halls” or “accomodations”, ie. Housing, are “catered” with a hot dinner, but it’s nothing like the lavish cafeterias Americans are used to.) Students may only have 8-9 hours of “module”/ “class” a week and are expected to work on their own - British students are used to that from GCSEs and especially A Levels.
I’m not sure I’d send an American freshman there unless they’re comfortable living on their own and have lived in a big city before.