Aldi nappies and wipes are super cheap and good quality.
Primark clothes are lovely and really good prices. Absolutely nothing wrong with supermarket clothes. There's some gorgeous stuff available.
Breastfeeding is free if you want to do it! Found this a huge bonus for us!
Second hand cot, travel system, etc.
I would go brand new for your car seat and cot mattress.
Don't get sucked into buying expensive 'Nursery sets' from Mothercare that cost £££. IKEA do perfectly nice wardrobes, drawers and cots for very reasonable prices. You don't need a change table or specific baby furniture or rocking chair. Just anything you can afford/have is fine!
I bought all my big buys on sale. Saves £100s! It seems expensive now but once you've got the big bits - travel system, cot - you really don't need to spend much! Plus you'll get £80 child benefit every 4 weeks. I put this aside for clothes, nappies, wipes, and activities if there's anything left. It goes surprisingly far!