I started a new game, and did the DG questline first, choosing to be a vampire. However i would like to get the companions quests finished so they can be marked completed and then go back to being a vampire which my character was actually set up for. is there a possibility to do this orr should i just delete the save and all the work done and start afresh again..... ?

Yes. Serana can turn you back to Vampire Lord unlimited times You can complete you companions questline. Remember this if you wanna be Warewolf again after being Vampire Lord, Aela can turn you back to wolf only once! (I hate that why she can do it unlimited times like serana, this needs to be fixed).

Thank you for the quick answer villethx, i was going to be very gutted if i had to start over

Np. Hope this helped you I really hope they will add more ways become Warewolf