*Shakes fist impotently at other British Members of the board*
In actual fact there are quite a few train tunnels in Britain, frequently for things a great deal less grand than the rockies. On my weekly train ride to manchester I go through at least one tunnel. When I've been further afield toward Leeds, I've gone through several more, some of them quite long - though I would imagine that is relative compared to the trains through the Rockies. Often the hills and valley landscape of Northern England mean that it is easier to make a long tunnel through a hill than it is to find a way around it. So down south might not have them, but I assure you we do.
Of course, even further north is Scotland, though I'm not entirely sure what the situation is here. I went to the south of Scotland, and the landscape was a great deal more mountainous compared to the hills of Lancashire and Yorkshire, and obviously the case is far more extreme in the Scottish highlands. Whether or not this means more tunnels however, I couldn't really say. As far as my limited knowledge of train lines north of the boarder goes, there isn't nearly as much in the way of railway lines in Scotland as there is in England. Of course the lines going up to Fort William and Inverness have to go through a fair bit of mountainous terrain, so it would seem plausible that there would be more than the odd tunnel.
And, of course, Hogwarts is doubtless more isolated than either, so unless you can think of a better wizarding way of negotiating such problem as valleys, hills and mountains, it's fair to say you can expect a few.
For everything else you could ever need to know about train tunnels in the north of England, feel free to drop and email to Keefyborestheworldsenseless@departme...dtunnels.co.uk . Thanks for your time.