I just started Sea Lion a couple of days ago on Field Marshal level. First couple of scenarios went smoothly (btw - in my humble opinion this DLC is the best so far in terms of variety of tasks and missions - great job!) until Basildon scenario (it is in Dover path). In this scenario my troops have been slaughtered by countless and apparently immortal British

. Despite my thick defense lines British tanks just cut through my Panzers III's and IV's which were useless against Matildas and even enemy infantry was attacking and destroying my best tanks! (i.e. in one of the turns I lost 3 armored units which has never happened in last 3 years of playing this game!). On top of that game objectives change in mid game making the task even more difficult (btw I like difficult).
Do you have any good tactics for this scenario? Mine was to concentrate on the couple of cities and fortified positions around bridge on Thames leaving the rest of the map to enemy but it wasn't enough. Or maybe should I withdraw on the other bank of Thames and destroy enemy tanks when they try to pursue me to the other bank and then counter attack towards the end? My core forces are fairly balanced (1/4th of tanks, infantry, artillery and aircrafts) and they use best equipment possible so it is not like I have crappy units versus elite enemy units and in all previous games I had easily achieved major victory, that is why I was so shocked when they simply drove over my lines

.
So any tips?