Deposit paid and voucher issued for cycle to work scheme .
First you need to speak to your cycle to work scheme provider and inform them of the issue. Many providers allow for a change of supplier.
Next start communicating with the LBS in writing, email, letter or both. Outline all the details and in particular the agreed delivery date. You are legally entitled to request a refund if they fail to deliver within 30 days of purchase or by an agreed delivery date.
If they refuse you need to follow their complaints procedure, assuming they have one.
Depending on how you payed you can use the charge back scheme for Direct Debit you have 120 days from point of payment to make the claim through your bank. If you used a credit card you can use the charge back scheme for amounts up to £100 above that you need to make a section 75 claim through your card provider.
I can't stress enough to try and keep things amicable, don't make threats but be firm. There are free online templates for these letters.
Contact your local trading standards for advice.
Read up on the law most retailers won't have a good understanding of your rights so if it turns legal it's best you do. You are protected under the Consumer Rights Act 2015
www.legislation.gov.uk
I hope you get sorted soon and get your bike.
Sam