I assume that your voucher has been authorized and issued by your employer based on a quote of £1000 from your chosen shop.
Don’t forget this is a legally binding agreement you are entering into and you will not own the bike until you finish the hire period and then pay a fair market value price, if the voucher is for £1000 you will have to pay 25%. The way you are going about this seems a bit cack-handed, not to mention fraudulent.
The only way to do what you want to do, in my opinion, is to be totally open with your employer, tell them what you want to do.
I’m just in the process of rolling the cyclescheme out at my place of employment and from what I have learnt it seems to be a very flexible scheme as long as you stick to the rules.