it hink in out grievence proceedure if its with another member of staff you are asked to resolve this informally int he first instance. however if its with a manager i think you would be justified going to HR and asking advice.
read through your flixi working policy and make sure that your manager is indeed abiding by company policy by not offreing you this.
where i work the hr dept has just made a big thing about introducing flexi working, part time, even 3 months off unpaid leave if you have a family emergency. - you have to "apply" fro this by filling in a form.
do you have to do this? when its in writing the subject becomes more formal and cannot be pushed under the carpet.
also you can always play " my brains mushed i've had a baby" card. ring HR as i am presuming you do not have access to the policies as you havent started work yet.
have an informal light hearted chat and ask what options you have.
ask them if they could e - mail it to your private account so you can read through it. the likley hood is the mail will read
dearxxxxx,
as per our conversation today please find enclosed a copy of our flexi policy. as we discussed you are eligable for xxx working practices.
or something similar - that way you have it in writing.
join a union. i think you have to be a member for 3 months and then you can ring them up and ask advice over the phone.
if you work for a big company the very LAST thing they want is to be taken to court for discrimination becuae you have a child.