OK - depending which visa you're on can make a huge difference to you long-term. DH was on an H1B. That meant I wasn't allowed to do anything, even voluntary work, and we couldn't apply for a different type of visa without leaving the country and starting again. But it also meant that his company had to pay for the green card application.
DTW now has 3 flights a day, 2 by Delta and 1 by Virgin. They're direct to Heathrow. They're also pretty expensive - around $1,400 to $2,000 return each.
Flying out of Canada is way cheaper, about $500, but you'd need to check whether your visa allows you to re-enter via Canada. You also need permission to travel through Canada (go the Canadian website and apply online, it literally takes minutes, but you HAVE to have it).
Around Detroit there are some really nice places to live, you can use a website like 42.3475,-83.1306 42.3475,-83.1306 42.234,-83.4815 42.234,-83.4815 42.3475))&offset=1000&count=1000 this to get an idea.
While you're in the US ask a realtor if you can view some properties just to get your eye in. Housing is very different and what looks like a 'nice' area for the UK could be quite rough for the US as houses and cars etc are so much cheaper.
It sounds like you don't have to worry about school districts, but if it's in any way a possibility, check the school district carefully. It's an absolute cut-off by geography, so one house on a street could be for one school, and across the road could be for another. Schools are funded by the property taxes in an area so low taxes = low funding for schools. Only about 25% of people living in Detroit send their kids to state schools and they are quite literally falling apart, so don't get into the Detroit school district.
Personally I really like Northville and Royal Oak. Ypsilanti is very mixed. There's a big college there so some liberal middle class areas, but also shootings on a fairly regular basis. Some people live as far out as Brighton, but it would be quite a drive. Ann Arbor is lovely but would give you quite an urban drive through traffic.
When University of Michigan (UofM) has a football game, traffic is crazy. It's the 3rd biggest seated venue in the world - over 100,000 seats, but football is in the fall so not something to think about now.
And the winters are really cold - be prepared for -20C for a week or two at a time!