First you need to check what the deal is with your IVA and the PCP payments .... many arrangements anticipate at the start, and include in the agreed terms, that the monthly IVA payment will increase by the PCP amount, when the PCP ends.
With regard to BH - I have seen instances where they have been 'happy' to ignore an IVA, but, be prepared for a refusal if they carry out a fresh credit check. We have had a post, very recently, where a BH customer was threatened with cancellation and repossession part way through the PCP because they were had entered an IVA. Although, this could have been an error on the part of BH, we never heard back from the poster with the outcome.
I imagine a 'bad credit' finance company would cost far more than the current PCP. I am also mindful of the fact that this option would be clear cut credit, which the IP would have to sanction first ---- I imagine they would also have to sanction a PCP agreement, even though it is not strictly 'credit' (and especially so if the first paragraph of this response applies).
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014