If you still plan to go to Germany:
everything will be completely closed at 25th, 26th of December and 1st of January. Whole day!
24th and 31st of December: only half days for shops, other attractions might be closed (germans celebrate Christmas on the 24th in the evening, that's when we get our presents.
It will be high season, if you plan to go, definetly check hotels now!! and make reservations!
The received wisdom is "Don't even think about it"
One factor not mentioned is the unreliability of the weather.
Frequently weather in both London and Paris is very similar. - if you do want to see more than one city, then surely London and Paris on an openjaw ticket but your best option is a single country, maybe including the People's Republic of Yorkshire.
Edited by: Grahamapoole
I agree it sounds rediculous but if you insist on seeing all four then you could consider flying into Dublin, then fly to London, take Eurostar London to Paris (quicker than flying and book it now!) also nice to look out of the window. Then train onto Germany and fly out from there. However that'll only be west Germany.
I went to Bruge for Christmas once and it was really nice, there were even shops open on the 25th, owing to the main celelbrations being on 24th!
To be honest you won't want to see much of the countryside at that time of year. Best to concentrate on UK with trip to Paris (ideally at end or beginning) and save the rest for another trip!
one thing no one has mentioned - the lack of daylight hours. Gets dark around 4.00 p.m. and light around 8.00ish.
Finding the cheapest flights to Europe requires multiple and sometimes-concurrent Internet searches. For travel flexibility avoid peak summer travel months or being enrolled as a full-time student may produce the best rates available. Because sales and deals can appear quickly, a different search platform can produce the cheapest European ticket with each new search. The same website or method may not work twice in a row.