You can use the green slip.
If you have a mate with trader's insurance you can use that. I just taxed my new golf using the trader's insurance as it covers any driver. Most insurance companies will email you the certificate (or let you download online) now too. Print off at home and this is still a legal copy.
MOT certificate.
Cash.
Job Done.
P.S. I am insured but the trader offered to help and that saved me from driving home for my certificate with no tax...