Stay with me on this one!
On the whole, EX can be a good dad however the majority of the time he's a dictator who can't recall anything he's said and in complete denial and full of contradictions.
Current situ - I work 2 days a week over a 7 day working pattern, no 2 weeks have the same working days. The latest I officially work is 6pm though sometimes it's later, because I'm customer facing.
DC started senior school in September and no longer wants to go to the child minder, understandably. Between us, ex and I said DC would go home after school and be alone (on the days I work) and ex would pick DC up, take to his and I would collect after work.
This week EX says he will be working late (on day I'm working), so I made provisions for a friend to have DC (her DC and mine friends since pre-school) however her DC had a gym session booked so my DC would sit with her whilst hers was exercising (no space for my DC).
EX picks up DC, takes home and then to football training - all as agreed.
Today EX phones and says this arrangement with my job's hours unsettles our child and that I HAVE TO change my job! In the 5 years since we've split, he's periodically asked when I'm going F/T (with the most recent time me pointing out his lack of parental support growing up) and that I didn't want to re-create this with our DC, hence the P/T job role. As usual, he claims no recollection of ever asking me about working F/T. I'm sure he thinks then he'll pay less maintenance as he moans about the amount he pays (which is a lot less than CSA website, but that's another thread all together)!
He then suggests I move into full time work, Monday - Friday and 9-5 (he lives in an ideal world) as he thinks this is better for our DC. I'm sure you're with me when I say this would be offering less support for our DC?! He then says that he can't take our DC to his swimming class at the weekend as "I work most weekends". I tried to point out that if I work 2 days in the week I then don't work weekends (as he clearly failed to see this when he made the statement)!
Anyway, even though we're no longer together he's still trying to control me and says that if he changes his hours of work, so he can be there with our DC after school, he'll then have custody of our DC. This of course then made me somewhat defensive so I gave him both barrels. 
So, WAIBU to tell him to do one and is this situation enough grounds for him to fight for custody of our DC?
Thanks mumsnetters!