Audio Extasa Vintage Hi-Fi
Decibel Hi-Fi Second-Hand Kit
2nd Hand Hi-Fi – UK Based
Classic H-Fi for Old Skool charm
Naimlylinn – Second Hand Naim and Linn Hi-Fi in the UK
The Vintage Knob – Hi-Fi Research. This site is great for research if you are looking for a component but cant recall a model number. There are often really good reviews of components.