Like my fellow UK residents, I must say that I find teh date a bit daring. DOn't get me wrong, I am sure te itinerary is nce, but I would recommend it probably for something very aware of what it will be.
- the weather can be anything form very nice (though dn't expect any high temperature for that month) to miserable with lots of rain all time long.
- British cities are a mixed thing for me ; it is full of history but some cities can be pretty ugly and do not have the feel of an Italian riviera city for instance - it can be very rough and industrial, just be aware of that as it is not your typical shore excursion. Countryside is glorious, if you like it.
- I think Britian is oneof those countries that is better visited by road, again as countryside can be absolutely glorious.
- regarding Le Havre, which is Normany, please note that it iwll take you at least 2.5 hours to go to Paris, so I would reocmmend any visitor to find an alternative and keep Paris for a separate visit and make some justice ot the city. Le Havre in itself was totally destroyed during WW2 so don't expect anything pretty. Outside Normandy is absolutely gorgeous though.
Overall I think it is one of those destinations that is probably more adult, and maybe woudl be better replaced by a roadtrip, where you'll have the opportunity to see London, Oxford or Bath, and take some time when in Scotland to see the Highlands and Lochs around.