Pregnant and working uk advice please

Basically I'm 24 weeks and a support worker. They've been really good so far accomadating to my demands. Anyways because I'm going on maternity leave end of October, and not returning, I've moved to a house about 40 mins away (though morning traffic makes it much longer).

So next week I've had my shifts through and for one shift they have put me down with a student at a different campus (and a 51 minute drive) and then the other day working 9-4:45 instead if until 4.

Am I in my rights to complain about or refuse any of these?

Technically we are paid for 9-4.36 but they always let us go at 4 and we support until 4.

Thanks guys