I found lose dresses (1 size or 2 sizes bigger) from Shein and some leggings worked a charm for me, they're so cheap on Shein and I can even use some of these dresses after giving birth too, they're just more "floaty" now I found H&M too expensive for something I'll only wear a couple months...
I’ve just bought some regular jumper dresses which have quite a lot of give, but also struggling to find much else on the high street… I’ll maybe try Jojo Maman Bebe as Silvia suggests
What size are you looking for? I've got a bunch of stuff I was going to take to the charity shop that you'd be welcome to if it would fit. A mix of sort of 12/14 sizes I think. Dresses mainly. No worries if it wouldn't be useful xxx
In Edin, JoJo Maman and H and M were the only in person places I found anything xxx
H&M on Princes' street and Jojo Maman Bebe