In reply to Tigger:
You'll probably be fine with what you have as long as you aren't camping out. A pair of hiking trousers with longjohns under is surprisingly warm in cold dry conditions. Two pairs of longjohns or 1 pair and some cheap microfleece troos under the the hiking trousers and you'll be really fine.
If you've got some money to spend, get a nice warm duvet jacket that you can pull on over your goretex or use alone if its really cold and you are not working too hard.
In Lapland for about the next three Xmonths at least to go 'hiking' you'll need to be XC skiing (or snowshoeing if you want to make life hard for yourself!).
Have fun - I've not been to that part of Lapland but it's meant to be really nice, not very mountainous though!