next were really good - not the cheapest but the 4 things i had from them lasted from about 15 weeks til well.....a few weeks ago haha
they are also quite big fitting so loads of room to grow
i also had a few less pricey nice things from new look but they didn't last over a couple of months. as for underwear i think i just got bigger sizes of granny knickers from tesco in the end
like others said, leggings in just a larger size would do (although i went for over the bump ones in the end as i hated things being across/under my tummy) and jumper dresses - from tesco/new look were the comfiest option for a long time, and for afterwards