book the car in for an mot, that will cover the tax and mot. then its just insurance, either take out temporary cover or risk it driving on your policy if its still covered under the old owners policy and he is happy to say its still his if the police do stop you.

its a bit of a pain, was in a similar situation when i bought my t5, no tax, mot or insurance on it, i just transferred my insurance over when i bought it then drove it 40 miles the mot station then home.