Whatever you do, don't get wheelbenders of any shape or form. Wheelbenders are things that grip only the front wheel (or, sometimes, both wheels but with no way of securing the frame). And sometimes not even that (depending on wheel thickness). They provide virtually no security and don't support the bicycle, so are worse than useless. The Tusk website has some examples - avoid!
Some of the vertical cycle parking is very difficult for women and shorter cyclists to use, as they assume that users are (a) tall and (b) physically strong. If the company is trying to encourage staff to cycle, and a broader range of staff to cycle, vertical cycle parking is best avoided for this reason.
Josta cycle stands (double decker parking) seem well used in some London locations including some stations. Cycle-Works supply these. They do ideally need to be covered, because of moving parts.
Sheffield stands are probably the best bet as a general solution and have the advantage of being simple and inexpensive. They need to be strong, and properly secured into the ground preferably using anchor security bolts. Make sure they're far enough apart that bicycles can be 'double parked' - one bike on each side of the stand - unless you for some reason (e.g. unusually absent-minded staff) feel the need to insist on single parking, which would take up more space. London Cycling Design Standards suggests 1-1.2m spacing between sheffield stands. If people use panniers for lunchtime shopping etc., the more generous spacing will be appreciated by cyclists.
As well as between stands, you need plenty of space 'in front of' and 'behind' stands, so that it's easy to access them with a bicycle. Bear in mind that a standard bicycle is 1.8m long. Extra length is needed to accommodate non-standard bicycles such as tandems (2.4m overall length) and tag-a-longs (2.75m overall length, dimensions from DfT 'Cycle Infrastructure Design', LTN 2/08). LTN 2/08 also gives minimum turning circles for conventional and non-standard bicycles, see Table 2.4. Chapter 11 of this also has some good summary info on cycle parking and what to think about when planning it - the whole document's available at:
http://www2.dft.gov....otes/ltn208.pdf
Access to cycle parking is often overlooked, e.g. providing dropped kerbs will make it physically easier to get to the parking facility. Signs are also helpful, and the company's website should have information for visitors on cycle parking; will there be separate visitor cycle parking? Again, that's often forgotten about.
For very short-stay cycle parking e.g. cycle couriers popping in reception with a delivery, Oxford rings can be good if there's a suitable wall next to the front door. Toast-rack cycle parking's OK too for visitors, as long as it's properly secured. Cycle hoops are a good new solution, especially for visitor parking, or where you need some cycle parking provision but have very limited space. Lots of them appearing on streets in London. Their big selling point is that they can be located on existing poles/bollards etc.
http://www.cyclehoop.com/
Location is critical. If stands are tucked away out of sight they invite theft and vandalism - unless in a secure swipe card-access area - which in practice means access to staff only or visitors by arrangement. (Most visitors won't wish to be bothered with the faff, which is where highly visible cycle parking comes into play). In general, unless the location is fully secure it's better to have cycle parking highly visible, and positioned adjacent to the building's main entrance (excellent statement of company commitment to sustainability, corporate social responsibility, etc.).
For larger buildings it may be sensible to have distributed cycle parking so that people don't have to lug panniers etc. a long way to their office.
Hope this helps - sorry if some of this is stating the obvious!
