If the services (ie course) doesn't start until January and you didn't pay until December then there really should be no problem (Vat wise) with them issuing you a new invoice with the lower VAT rate. They will not be out of pocket at all (they collect the VAT from you and pass on to Customs) so this really shouldn't be a problem. Worth persuing ! (It gets more complicated if payment was made in November - but still worth asking the question again). Best of luck !
