I am an ops controller at a handling agent at MAN (not Serisair). I was working the night in question. All of our Southbound and Continent bound flights were imediately badly affected by slot delays. In our case, flights that were due to depart at say 5ish were copping for 7 hour slots. That was the case for about 45 minutes after the initial failure of Swanwick. After they got back online however(much quicker than initially expected), I spoke to ATC who informed me thay were allowing southbound slot delayed flights to depart, on a first come first serve basis with 6 minute route separation. The slots however are issued from Brussels and they were not ammending them (the slots). SO all we COULD do was to call the pax back to the gate, get them on as quick as possible and hope for the best. Sometimes you win and sometimes you ride out a ****ty slot.
Not the handling agents fault at all.