I micro-managed my migration and kept in almost weekly communication with both the loosing and gaining ISP.
I was very upfront on what I wanted. I asked for 30 days cancellation and agreed a termination date with BE. When that the migration failed (3 weeks late) I rang up BE and asked for a later termination date. And it all worked out fine. But I paid for about 45 days service instead of 30.
It'd be nice if migration was as straightforward as ISP blurb would have us believe.
Plusnet unlimited FTTC