Don't know about the other days you mentioned but today's SN cancellations are weather related, both arrivals cancelled today (meaning tomorrow's 06.20 is) as well as a BE110 from AMS due 18.20. I see the Jet2 Grenoble diverted away from BHX as well and a whole host of flights this afternoon and evening are delayed due to earlier strong winds.
I don't know of any other reasons why there have been so many SN cancellations recently, I can only assume it's related to the CR9 whereby the knock on effects of disruption are more difficult to catch up with than with the SN mainline fleet. SN are treating BHX with the shabby end of the stick for a route that always shows consistely high fares and has good LF's.
I'm guessing your on a mileage burn trip or are there no LPA flights on the day you want to fly?