Couple of ideas....
Ipswich win play offs as only team that have qualified for final....
Poole win the title as league winners
Or Poole v Ipswich final as Poole league winners and Ipswich play off finalists.
(Bit like in golf when you hit a 2nd tee shot im case you can't find the 1st in the rough)
Or single Play Off Final at a neutral venue e.g. Peterboro (afterall not as though Buster will allow it to be at the National Speedway Stadium)