I think M&P is on the big size. Also have a Dorothy Perkins pair of jeans that are on the large side even though I'm in late stage of pregnancy.
i'm just living in my topshop pair of skinny jeans. every day. when they're in the laundry, I wear my low waisted regular jeans with an extender or hair elastic.
i just found out my sis has sent me some of her maternity clothes including some 'expensive' jeans. have no clue what brand but from the US. looking forward to a new, free maternity wardrobe. should arrive on Tues with DH's return from his trip to Baltimore.
about nighties, i got some cheap long tshirt dresses from H&M that did the job last time. for BF, I do prefer a tshirt I can lift up which, for me, is more discreet than a front opening. but i'm very shy about feeding in front of others ( i won't do it in front of in laws and certain friends).