Subtlemouse, i think that coun'ts as a genuine reason to use a disabled toilet, it is an illness that if there is a que will prevent you to use a regular toilet, i wouldn't have a problem with that.
In our M&S people just use whatever toilet is availiable regardless of wether they are disabled or not, a young lady was waiting outside the disabled toilet with someone else the other day and said, 'oh i can just use this one then i can take dd in with me'
I said to her 'Sorry but my ds is actually disabled and desperatley needs the toilet, can he go first?' Thus was confirmed by DS crying holding his bottom becuase he really needed to go.
She said 'no' and DS had an acident which really upset him.
I am going to buy a radar key i didn't know you could buy them, i really get annoyed with non-disabled people using the disabled toilets, but........ SOmetimes you can't tell if they do have a genuine problem, my mum for instance needs the bars next to the toilet to get on and off as she finds it hard with a bad heart condition, ds isn't visibaly disabled with his shirt on but he can't wait for a toilet and on a bad day needs lifting on so the extra room in important.
If there isn't enought room for you and your buggy, go and complain or leave the buggy outside and just take baby in, i can manage it so can you.