First of all, i don’t think Germany should upgrade the UK IC (and in Alpha rules it even isn’t allowed).
Aas Germany you should at least make he impression to fight for London (to make USA send alot of troops), and the moment before they’re going to get slaughtered, germans can chose to pull back (if the situation is hopeless), or (if they think they can hurt the attackers) stay and fight for it.
Eevry turn UK doesn’t have London it’s about 20 Allied IPC less per round. That’s not nothing, so every turn you can stretch this is good. Also Italy can benefit a lot from the british downfall.
If you plan a counter attack against liberating americans, leave your troops in London and load up for a counter-counter-strike.
USA should know that if it liberates UK, it has to make sure they keep it for 2 turns at least (since 1st turn UK cannot buy but gets money, and that could be looted by Germany again).
If they do, german’s time in London is over, if they make the mistake of rushing to take back UK (and most players will probabaly fall for it once - i did…), germany can play with them.
I think it’s best for germany to spend abit on it, as it is good to delay Allied actions (winning valuable turns and keeping the Allies weakened - can also be good for Japan by the way), but other targets (Russia!) ought to be their top priority.
In the End, London IS a VC (a means to win the game) and though you can’t count too much on keeping it the whole game, you don’t just give it back! You use it and meanwhile you go for the other VC’s.
