Don't forget that "you and me" can be perfectly correct when it is not the subject of the sentence.
For instance, "He's going to drive you and me to the shops" is correct.
I have an inlaw who was a primary school teacher, and is forever correcting the family (adults as well as children) on how they should speak, but she has had 'you and I' so drummed into her that she frequently uses it when she shouldn't!
The way you were taught to get it right, Esspee, works well in the present tense, but not so well in all tenses.
For instance, If someone said, 'My friend and me /me and my friend were watching a film', it wouldn't help, as we can say neither me were watching nor I were watching.
Personally, I know the 'rules' but, perhaps because of where I grew up, feel slightly awkward saying thinks like My husband and I ..., You and I ... etc.
They can sound rather affected in many settings, and I often deliberately choose to use Me and my husband etc., instead, depending on the setting.