would u b upset to find...

[NILBY]

OH reduced payments into the joint account by £100 a month for months without consultation?
OH had compensated at the time by paying £100 towards DD's nursery fee's. I had been paying all the fees before that...
Im i going bonkers or has OH not paid a thing?

your other half started paying £100 towards your daughters nursery fees instead of straight into your joint account.

there is surely no difference if you were paying the fees out of that account anyway

he has just been paying the money to you in a different way

Your ex has paid the missing £100 via a different route (nursery fees). He has still been paying it.

At the end of the month your financial situation will be the same as if he had put the money into your account.

ahhh hang on, perhaps we're all missing a point here.
perhapos the OP's other half has "generously" offered to pay this £100 worth of nursery fees. OP assumed that this would happen as well as the £100 going into the account each month, but he has secretly stopped that.

so he isn't paying anything extra no. you're exactly the same as you were before