May sound strange but charity shops and car boot sales can be great for film findings.
I've seen people selling the old minolta rokkor MD/MC lenses which are great quality and you will need an adapter for your camera but they are cheap as chips and people are pretty much giving them away at car boots. eBay can be great for availability but price is a downside because people know what they are worth, same goes for places like ffordes where they can charge considerably more than eBay however you are working with a shop and you get a warranty and if there is a problem they will sort it out so I would say it's worth the money in the end buying from a reputable dealer.