It's not the best suggestion, but just get canny about buying non-maternity clothes that will work. You will find the odd maternity thing, so keep your eye on ASOS and H&M for long tops, say. And if you wear jeans I think it's worth investing in a good pair of maternity ones with a stretchy waistband (Seraphine are good).
But otherwise, buy a few roomier things from the mainlines and make do. Eg I got a cocoony car coat that covered me for the last of my pregnancy (November baby) and looks lovely still. Maternity leggings are a wash, they just slide down, you need a proper wasitband to hold the damn things up! - just go for something thick and wear under your belly (these M&S ones are good, order in advance and get the delivered to store for free, they never have them in). Stretchy dresses are great, you just end up wearing them like tunics / tops. And I found that cardigans and jackets fit me like before, just no chance of doing them up 
Get a comfy wire free bra, my Bravado silk seamless ones were amazing, really comfy to sleep in and gave good shape whatever the size of my breasts, wore them all through pregnancy and BFing, they wash brilliantly, and then they convert to a normal bra (though you'll want to burn the damn thing at that point). They come in small, medium, large, rather than specific sizes, and really do cover a multitude of sins.
And since that's all so fecking boring, throw yourself into the world of accessories!