Definitely seconding Goldhawk Road - that's where we always hit up first to check for fabrics, and to get ideas. Keep in mind that in a lot of the shops there they don't display prices on the fabrics, so you can barter prices. They will also sometimes try and sell it higher than normal, so keep in mind what the fabric is worth and be firm. Some of the attendants can also be a bit pushy (and very unhelpful! i.e. ask for light blue and they show you navy...) just say "I'm just looking" and ignore them until you have questions or want to pay

You can have amazingly cheap finds here, I bought the material for
this costume for £1 a metre.
For Tooting, Amy-Lou and I check there for more standard fabrics. Goldhawk Road is brilliant for amazing fabrics, PVC/Leathers and weird stuff you never imagined - but sometimes finding something like simple cotton in a specific colour can be hard. We head to the craft store just by Tooting Bec station -
here's their website. Decent range of materials, but lots of sewing supplies (zips, threads, fastenings) and craft supplies (funky foam, paint, feathers, etc). Down in Tooting Broadway market there's a few stalls, and many sari shops up the main road heading to Tooting Bec, but often you can get better stock in Gold Hawk Road.
For art supplies, there are tonnes of shops around central (London Graphics Center, Cass Art, Cowling & Wilcox, etc) where you can pick up paint & foam. Often if you know what you want, it's sometimes cheaper online
For specialist craft supplies (resin, plastics, metalwork etc) check out 4D model shop, near Aldgate - they have awesome things that I always want to buy and play with.
Wig heads - any costume store will normally sell them for £3-4, failing that, Ebay can be cheaper!
There's lots of us based in London with different knowledge, so I'm sure if you can't find something one of us will be able to point you in the right direction. Lastly, welcome to London!
