I'd actually been past their building a few times but never stopped, because it doesn't look like they have any kind of trade counter. What's more, you always feel a bit silly asking for one or two components in a place that deals in bulk quantities. However a lady on the phone told me that they do serve customers on site, so I popped over there this morning.
The building was once rather posh but now looks run down. I couldn't actually get in because the door was locked, but after a while someone came to open it. Inside there is a semi-derelict waiting room and not a lot else, but the chap confirmed I could buy stuff and went off to find his supervisor. After a while a lady came and took my list, then a lotof time passed while they found the things I wanted. Obviously by this point I had decided that it would be quicker and easier to just use the website in future.
Then the lady reappeared with the buffer chips - and said I could have them for nothing as they are closing down shortly.

So anyway... I asked whether they are still taking website orders, and basically they are - but not for much longer (until June I think). If you need any items which are only available from Quarndon (or if you're in a position to negotiate a deal on a lot of stuff), I suggest you get in touch with them.