Fit components without names. No name stems, bars, seatpost, etc. I found black electrical taping over the decals works, and after its baked in the sun and had some rain on it its a pain in the a*se to remove. Slick cheap tyres if its a mountainbike, basic V brakes, singlespeed, no shiny shiny parts. Chavs are like magpies, they like shiny things. As someone said replace QR’s with allen key bolted things, same on the seatpost. Also, keep your brakes tight, so tight that even if they do undo the allen key bolt QR’s they cant undo the brakes to get the wheel out. Its all extra time that may make them give up. Big thick D locks tends to work, but also gives it the impression its worth nicking. I tend to find a thickish cable and motorbike disk brake lock (looks like a tiny D lock) works well and is more flexible. Finally, dark plain colours are best. Dark browns, blues and blacks. Bright colours are the fashion (as above) and instantly draw attention to it.