I am rubbish at links so forgive me if they dont work - you might have to cut and paste, but I have just been buying stuff.
www.seraphine.co.uk - pricey but the sale pages for bargains and treats (I had to have some of their jeans as they are so nice)
www.heavenlybump.co.uk some heinous, but some lovely tops and dresses too and its really lovely quality. Sizes, like all maternity clothes, on the biggish size.
www.jojomamanbebe.co.uk Some good priced tops and dresses although some stuff is expensive. Mumsnet usually have a voucher code for 10% off in their partner offers.
www.bumpsmaternity.com/Maternity-Clothes.html some pricey, but some bargains on sale nearly all the time
In store I got some lovely shorts, trousers and dresses from New Look - not a shop I normally go to, but they had some good stuff. There is some stuff just online, so worth a look. Online seemed nicer than in the shops. Sizes come up big.
I also got some nice stuff from H&M, I love their vests particularly and got a gorgeous maternity swimsuit that is super flattering.
Dorothy Perkins has some nice dresses if you need summer work stuff.
Can you tell I am a tad obsessed?