I would book the IM and depending on what happens, if you need to transfer to a hospital, see if you can transfer to a closer one with her acting as your doula. Otherwise, you're definitely heading for a hospital birth anyway. Irrespective of what hospital you end up in, I always recommend having an IM with you - not just for the birth but for postnatal care as well.

When planning a homebirth, I believe in having 3 birth plans. 1 for birthing at home and 2 for transferring (1 for VB and 1 for CS). If you plan for the possible outcomes then you will feel more empowered no matter where you birth. (btw, I believe in having 2 birth plans for hospital births as well)