I buy from Boltbase, usually via Ebay, though direct for larger orders. There's plenty of ebay choice, I like the detail this supplier provides, the delivery has always been correct and prompt.
I do wonder how welcome my custom is at a local fixings place, I've had decent and friendly service, though they haven't always had what I was looking for. It strikes me that by the time they've taken the cost and processing out there can't be any profit in my fiver order, a few bolts is often even less and it doesn't account for when they've spent a bit of time with me and I haven't bought anything. I know from working in a different field (PC components) that online sales take a tiny percentage of time compared to counter sales, there they were happy to spend time making sure you had the right connectors for a couple of quid, because there was a chance you'd be back to spend several hundred, but that isn't going to happen with my fixings shopping.