Well I've phoned DVLA, and they've confirmed I can't tax the car immediately as theirs no V5 or V5C, and the vehicle is still registered in the previous owners name.

They've advised me I need to apply for a new V5 by filling in a V62 and sending through to DVLA with £25 cheque. Then it will then take up to 30 days, and then a new V5 should be issued. TBH I'm not too fused about waiting, as long as a new V5 is guaranteed, it will give me time to sort the issues. I'll keep my diesel for 30 days and when new V5 come through, I'm on the road.

As long as the dealer will deliver I'm happy with this. Only concern is if theirs any dispute over owner ship, but I phoned the original auctioneers which is a very large national Francise, and they went through everything confirming the I could by the car, and be 100% legal owner.