Keep your eyes open at your local friendly German discounter. They often have selection packs for a couple of pounds, and because they like to be able to quote huge numbers of parts the smaller sizes are well represented, which is good news for electronics and light DIY. I have a few of these, you can get 600 piece sets for a fiver. In there will be M3, M4, M5, M6 and probably a few M2.5s to make up the numbers, in various lengths and maybe 2 different head styles. You’ll get nuts, bolts and washers, maybe Nylocks and certainly a good few spring washers. As I say I’ve had loads of these, my latest was something like 200 stainless steel wood screws for £2 or £3, in a selection box. It saves all the buggering about, I had a bit of shed blow off last week in the storm, the fix was to get a few screws out of the box and wind them in. It took 5 minutes, compared to traipsing off the B&Q and handing over a pound for half a dozen fasteners. Similarly when something falls off the bike or car you can just discard any corroded broken or damaged fasteners and replace with new. At least you know they will screw in without jamming.
