I've done several hills with signposts showing 14% and I've found that the perceived gradient varies greatly...
For example, a 14% hill near Owslebury is fine:
But the 14% White Hill out of Pitton feels much steeper:
But the hill between West Dean and Whiteparish is signed as "only" 12% but it's much longer and is probably the hardest climb I've done in Hampshire. (Do you know of anything harder?)
25% should be in another league entirely. Blissford Hill, just north of Frogham in the New Forest, is 1-in-4 although apparently it is quite short. It will shortly be on the agenda for a cycling trip.