Advice for France/UK trip - too ambitious?

2 1/2 days in London won't even begin to scratch the surface of all there is to see there. I would add another day and not think of doing any day trips from London. And if you were doing a day trip from London, I can think of better places than Canterbury, unless it's a pilgrimage site for you.

Could you start in Strasbourg and then head to Paris? That would a better use of your time, in my opinion.

You're looking at 4-5 hours, minimum, drive each way to Mont St Michel from Paris. Plus you need to time your arrival so that the causeway is above water to get there. That's a very long day. And taking another day just to run down to Strasbourg just isn't worth it in my opinion. There's a lot more attractive places to explore closer. You might want to consider just doing Paris, Normandy, and those areas for your week.

Agree with others not to add in day trips from London as there's loads to see here even if you had more time. For getting to Mont Saint-Michel, that is definitely doable as an overnight trip- there is a direct train to Dol De Bretagne from Montparnasse (2.5 hours) and then a bus which takes about half an hour. When I did it the bus timing linked up with the train, and we arrived before lunchtime. Staying overnight on the island itself is amazing as you get the whole place mostly to yourself in the evening/early morning. There's a bridge so you don't need to wait for the tides to cross onto the island, you can go at any time (either walking or by shuttle bus).

Personally I would choose Giverny over trying to get to Strasbourg, and Monet's garden is a wonderful place to visit. That's also a more realistic day trip. Good luck!

I guess you know you'll get a different opinion from everyone. My two cents:

April 6-8: Explore Paris, with one day dedicated to Versailles - My only suggestion is to leave yourself free to pick a good-weather day for Versailles. Oh, and say "bonjour" and "s'il vous plait" a lot.

April 9: One night at Mont Saint Michel - If I had a bucket list, that would be on it, but I guess I am content to have walked the causeway out to its little brother, St Michael's Mount in Cornwall.

April 11: Day trip to Strasbourg or Giverny (stay overnight?) - My wife and I made an easy day trip out of Paris to Alsace and back by train a few years ago. I found Strasbourg a bit workaday, but our little side jaunt down the valley to pretty Colmar was heavenly. Never been to Giverny, more's the pity.

The rest seems good. Eurostar to London? First class is worth the extra expense, and in case you are subject to motion sickness (as I am) and never rode a bullet rain before, be aware that speed is a factor. I'm OK if I look at the horizon the whole time.

Have fun.

I am not a huge fan of hub and spoke travel if it can be avoided. I would personally skip Strasbourg and do some route planning to and from MSM. There is a LOT to see in this region. Rouen could substitute for Strasbourg, and this also makes including Giverny easy. Then you have the Normandy beaches and towns, Loire etc. to complete your loop. Spend the night on MSM. It's a very different experience once the day trippers leave. All of this said, if you are set on only trekking out for MSM, then I found the TGV to Rennes plus a car rental to the island to be the most efficient use of time. Tides should no longer be a consideration for access. The causeway was replaced by a bridge a few years ago.