Hillarys blinds 10% off vouchers

eam2006

Hi ( my first post)
In the middle of October after shopping around I chose Hillarys to make made to measure blinds for 7 windows. Tomorrow the fitting takes place and the final 50% payment is made. However, I have received in the post 6 10% of vouchers from Hillarys for friends and family. Well I think this is a bit cheeky. I haven't got my blinds but they are offering 10% of for anyone that I give the vouchers to. The voucher states that the 10% may not be redeemed against any outstanding invoice. I rang the company and the guy at customer services said I had a point to be miffed but negotiate with the agent - who is coming tomorrow to fit the blinds. My question is how to approach the agent to try and get the 10% off! I know he won't want to do it. Do I have any grounds? If anyone wants a 10% off voucher let me know. As I haven't got my blinds yet I can't comment to much on the quality as I have just seen a small blind as this was what the agent brought round when he measured up. 10% is alot of £1100!
Thanks
eam