Claire,
At the southern tail end of Windermeer,( J36 M6 Lake district) there is the Haverthwaite to Lakeside railway. www.lakesiderailway.co.uk as for sites, take your pick.
Also while you are in the area, up the Cumbrian coast about an hour drive, at a beautiful place called Ravenglass, there is the la`l Ratty, it`s a narrow gauge railway that runs up the Exdale valley about 16 miles round trip, just put la`l ratty into google and you`ll get all info needed,
If you want more help with sites just ask
Tony A.