gumtree, these will all be local so you can arrange pick up rather than have to pay for postage
also freecycle is a site where people give things to others so they dont get thrown away and again has local sections-theres bound to be loads of baby stuff on there since they grow out of stuff so quickly
I also recommend gumtree since its all local so easy to pick up! and I have got some good bargains from it before since people are just wanting rid of the stuff they usually let it go for not much money plus you can haggle a bit of the price is too high!
Best of luck and well done for being sensible too many folk want to rush out and buy all new things for babies when they are going to outgrow everything so quickly!