FWIW - all ecommerce sites based in the uk must have one-click access to a point of contact, but that can be a postal address, telephone number, email, heck probably Telex if they've got one set up. If they don't have that, then I'll move on. I know this as fact from my job - I'm a web developer, done a few ecommerce sites in my time.
Any store that is well-set up or deals with me well will get my business. I tested Books On Board with a £3 purchase, and it went smoothly. IMO, not the most intuitive site, and slightly clunky purchasing/wishlist model, but it's worked every time for me. If I had a problem, I'd at least contact them direct, wait 48hrs (longer if a weekend) and see where it goes. No point flying off on one straight away.
Now Amazon... don't get me started on some books I ordered from them...
That bad deal cost them a Kindle, even though I'd ordered DTB's.