I have run around the map for a few times, I found that the Germans could be organized and win easily:
1. the first flags are undefendable, but it would be good to hold them as long as possible
2. never lose the cathedral flag, that flag not only locks 2 other flags but also provide a counterattack spawnpoint when marie is lost. Also, when holding cathedral flag the germans won't bleed even if all other flags are lost. You are actually defending 1+2 flags for the cathedral.
3. use the cathedral to monitor enemy armour movement, this would help tank busting a lot
4. always have the APC parked in some place hard to find yet potentially useful(for counterattacks), never drive the APC on the main roads.
5. without SL spawn, it's much more worthy defending the roads/manning emplacement MGs, and running randomly around is certainly not a good idea, since you no longer need to worry about taking out SLs in order to stop an attack.
6. S mines could be used as "CCTVs" to monitor enemy movements. Without SL spawn, the S mines could be useful decimating a sneak attack. (while with SL spawn they could just let a SM die when they saw such mines)
So, it is actually quite obvious how the brits should play, controlling the cathedral is halfway to victory.