See that written by the other DND? That's my old account.
Whilst I agree with most of what I've previously written I would add this.
Seasons 1-4 aren't quite carbon copies of the previous 3, it's more like the scripts have been sliced and diced and then pasted together in a random order with wee bits of additional stuff added to tie those bits together.
Calum Buchanan was a nice albeit brief addition.
James changes quite dramatically after the war (probably to be expected, though they really don't mention what transpired in the wartime years) and I don't really like him as much as I did before.
Siegfried, doesn't change at all; well apart from getting married (then having children) in the first of the Christmas specials; sadly his wife and kids are NEVER seen and seldomly mentioned again.
Helen is now played by Lynda Bellingham.
Tristan disappears for long periods, thankfully when he is around he still drinks like a fish and is aways chasing women.