thanks for all the pictures and replies
this is a very useful thread for people to refer to in the future as well i think
i have ordered a plaster one of ebay just to see what it's like
if it's a load of rubbish i'll probably get a woodland scenics one or try peco and cut the slides straight as was explained in above posts
you'd think scenecraft or hornby would make some decent tunnel mouth for n gauge! revolution / dapol / dj model or someone else maybe can take up this challenge. i can't see why it wouldn't be a success as all layouts pretty much have to go 'off scene' with a bridge or a tunnel... (or just a hole in the sky...)
i did see a laser cut ply or mdf kit for a tunnel as well but wasn't too keen
anyway i shall see what arrives in the post!
cheers for your replies - railsquid wins the most tunnel mouths in one picture prize...
tim