This is usual in the winter season. Flights to Luton seem to be only once a week or so. They never announce it, but when the summer comes they announce with great fanfare that "we have added 500 more weekly flights to Luton ..."

I think a change to UP is unlikely, as the business class is usually quite full going to Luton (I don't know about the return as I always return from LHR). The early morning flights are very convenient for business travellers.

In addition, I would not attach much importance to flights loaded onto the system more than 11 months ahead.