Bit of a niche this one. A Christmas Northern lights fly cruise departing on 18th December for 11 nights. It's with Hurtigruten and the same cruise direct is significantly more where Iglu have this with the flights from the UK included - although it doesn't say where from. I suspect it may be LGW.
The itinerary is in the screen shots below, which includes heading into the Arctic circle and Norway.
I've posted a couple of screen shots of some of the excursions from Hurtigruten website. In places like Tromso you could easily DIY excursions and you may also be able to compare prices with those you can get yourself in Port.
If you don't see the Northern Lights (they don't appear) you get a free 5/6 night cruise. This is also a no tipping cruise.