chester If you wait on people hand and foot, they come to expect it, Perhaps the first time they visited, you were being extra polite and now it has become the norm. Next time, don't. I don't mean you sit down and wait for them to do it all, but say casually "Could you give me a hand with taking these plates through, please?" or whatever, and then thank them for their help.
And be ready to drop into the conversation how tired you get, now that you have the baby to look after 24 hours a day.
It may be that she is hesitant to offer if you seem to have it under control - I know some women resent having someone else doing things in their home and Grans can feel that they are wrong if they do things and wrong if they don't.
I am not surprised your son screams when a strange face is shoved into his. Maybe you could say "He does like his own space, he doesn't like it too crowded" - that is, it is him who does not like it, it is not you being difficult.
You are very lucky in having had a helpful Granny coking for you, and an understanding "god-grandmother" round the corner, but do you think MIL could be feeling a bit pushed aside by them?
To think that London, or anywhere else for that matter, does not belong to any one demographic
What is a reasonable minimum spend for an online grocery delivery??