There have been many changes to the scheme over recent months and it is very important which scheme you choose or whether it is done in house.
I set up our scheme, and despite all the changes i DO believe that it is very worth while. Here is an overview of how ours works:
Company buys the cycle at full price and then claims back the VAT. Eg. Buy bike for £1,000 (max) and claim back 20% (£200).
You enter into a 12month hire agreement where £83.33 is deducted from your gross salary. Because this is your gross salary, when you pay NI contributions and income tax on your wage, this is now calculated on a smaller salary so you pay less. This will be either a 31% or 51% saving (approximate) depending on whether you are a standard or higher rate tax payer. (Note that 12x83.33=£1000 not £800. This is because after a legal change last year you now have to pay VAT on salary sacrifices).
After 12 payments my company gift the bike to you. (They've recovered the full £800 that they've paid out, and they've also syphoned the additional VAT payment to HMRC)
Because you received a gift that according to HMRC is worth £250,the company completes a P11d declaring your benefit in kind and your tax code for the following year is altered by £250. So you pay tax worth either £50 or £100 (std or hgr rate) spread over 12 months.
Total cost to you (Std rate taxpayer) 57.50x12=£690 + £50 = £740
Total cost to you (higher rate taxpayer) 42.50x12=£510 + £100 = £610
The figures speak for themselves on a £1k bike, especially because of the spread out payments.
The only thing you need to be wary of is C2W companies who insist on keeping ownership on the bike. They will cost you more as their profit will come out of your savings. I.e. they won't gift you the bike, they will make you pay more for it, and keep ownership of it for longer so that the residual value drops.
Hope this helps anyway - let me know if you have any more specific questions.