I would say if you want to buy everything new, go for it, plenty of people do. Equally lots of people get things from friends with children already, people are always delighted to offload their baby gear to you. But lots of local parents sell on their stuff on local websites/facebook pages too and usually for a song.
I bought a bugaboo chameleon 2nd hand, in perfect condition for around £200 when I had mine a few years back; lots of people sell buggies in great condition as when they have their second child, they move onto Phil & Teds and the like. From this site actually.
What I would buy second hand is baby clothes. There are so many in perfect condition, when you think they get worn for a few months at best.
I'd also get things like bumbos, babybaths, changing tables, moses baskets (less the mattress) nappy bins second hand. People are always selling those.
The first thing I would do is join SW11 Mums Buying/Selling/Giving facebook page and the SW18 one is also good. People are always selling things on there.
Secondly, get yourself to a nearly new sale, the NCT hold plenty, for example this one in Clapham on Sept 21
https://www.nct.org.uk/events/clapham-n ... new-sale-2
or this in Wimbledon
https://www.mum2mummarket.co.uk/london- ... sales.html
You can get lovely things, I got a lovely Ralph Lauren jacket for about £10 when my child was 18 months.
This website and the SW11 mums pages are great for new mums, whether it's about when to put names down for day care nurseries (before birth for some of them) or school & preschool (at birth), good local playgroups and classes etc so do use the resources available; it's not called Nappy Valley around here for nothing.