Fara kids in Primrose hill
I wud say if u buy new jus buy bigger a few essentials
Shopping malls should host a swap shop once every 3 months, would be such a good idea. I used to just buy bigger sizes of clothes that were cheap. Markets are good even though you can't try on. Walthamstow market is where i got some loose old fashioned night dresses for hospital and quite cheap as well. There should still be some markets, isn't there one in Petticoat lane?
Vinted - it’s amazing for maternity wear
Fara Kids Charity Shops normally have maternity sections, and there are several across London.
Try with vinted app
There are some boot fairs specifically for baby’s and mums you could search. I just chanced it and got all mine online. I hated not being able to try things.
I told my SO this is just the kind of shop i want to open! (rather than ho back to my job) i hate online shopping and struggled so hard to find stuff