I think the problem with somewhere like Munster is that it is in close proximity to the likes of Dortmund which have well established links to "London" airports. Given a choice between an hour on a train in Germany and just under an hour on a train in the UK, many Germans are likely to take the former, at least that was the tone of many of the comments made in the local press and FMO's Facebook page around the time of the announcement. I have no knowledge of the figures, but a quick look at the Flybe booking pages (and throughout the last month or so) reveals many flights still at or not too far above the base price. Not scientific I know, but hardly encouraging.
On the other hand, Rennes and Groningen seem much more promising. I have deep reservations about Antwerp however, particularly twice daily and with Cityjet continuing to offer flights to LCY.
In other news, the Dublin flight situation still seems as clear as mud with nothing available on the Aer Lingus website, so presumably that means the flights will be stopping in October. There are 8 rotations a week currently on the Flybe website but no provision to book through connections onto Aer Lingus transatlantic services and the announcement seems to have been spectacularly badly handled with nothing on the SEN website. The mid-morning arrival time for the weekday flights and only daily service means this will be of no use whatsoever to business travellers so presumably they are targeting tourists to and from Dublin only. A real shame.
More encouragingly, Skywork announced that they will move their Bern services to Southend from London City in October, although flights are not bookable. This should be a good bellwether to see how services go after moving from City, and whether they are able to tempt some of their (presumably mostly business) travellers to make the trip to the Essex riviera rather than using the Zurich to LCY services. Interesting times ahead...