Ask them for a refund, Jean, and your credit card company can take up the matter for you. You have signed for Euros so they have no leg to stand on, ask your CC company for immediate credit back on the account and they will sort it out is my advice.
On the wider topic of car hire, so many threads regarding various car hire options, it's a minefield of unhappy punters. The good local family companies charge more but you get guaranteed service and only pay what is expected. We must see posts like this every day on CDS forums from unhappy punters yet I've never seen compliants regarding the local guys.
Thankfully this is only £8 but annoying anyway.
With all the hassle involved in complaining I don't need it, I just pay for a good company and relax. I'm afraid niggles, complaints etc. go with the territory when tying down brokers and the big companies on price.
Anyway I hope you get compensation, Joan, I'd want the £8 + costs of persuing this, would suggest £25 compensation as a sorry for their mistake.
Edited: 6:04 am, November 16, 2012