If you've never been on skis before, I won't even try to take you out there on a pair of them. Cross country skiing with packs and/or a pulk or tobogan or whatver you will use, is not for beginners. Specially if it's the first time out there. And you will be going out more or less straight from the airport :-) Also it's not only the skis. You'll need ski boots that fit exactly, or you will be in a world of hurt with blisters etc. Susanne will confirm this for you :-)
So snow shoes for you I think.
And perhaps we have to start you somehwere closer to a road. But we have plenty of options here, with plenty of time to make a good plan, and most lakes here have fish in them. So we'll find a good spot for you. But the place I have in mind for camp is only a 1 km from the road, and half of that we'll be crossing a frozen lake. So the terrain is flat. So getting there should be manageable for most. But I must insit on snow shoes. We could be in 1 meter of fresh powder, or on a thin frozen crust over sludge. Or we'll be walking on a frozen crust of ice, capable of carrying us on foot in, but the next day we get milder weather, and we sink in to the hip. Impossible to know before we are there. I'll be on skis, but bringing snow shoes.
As for going with a train...that will take you around 24 hours from Oslo...to get to Fauske (near Bodø), where the tracks end. Thats 300km south of here. And then it's a 6 hour bus ride including a bus change and a 1 hour ferry crossing from there. And the bus only will cost you 70-100£. So it's not likely that it will save you anything, regardless how large a discount you get.
Else I have the car so we can go sight seeing. I have a second mountain area we can drive straight up to the top for a fantastic view. And if there is Aurora activity I suggest you spend at least one night up there. As light pollution up there is minimal.
Anyway, I think you'll have a good time. even if the wetaher turns nasty it should be an adventure for you if you come here with the right attitude :-)