Neither Derwentwater nor Coniston are as hard as Hawkshead but both do have significant climbs and 'their moments'. Derwentwater, for example, has basically only one climb - but its unrelenting for nearly four miles and traverses a bog before the steep bit at the end. If you go to the Lakelend Trails website and look at each set of pages for the different events, you'll see that the silhouette image at the bottom of the page differs in each case - that image at the bottom of the page is the race profile.
I'm sorry Daz - you and I will have to agree to disagree on this one - but I can't bring myself to call this a fell race, primarily because of the terrain. It was virtually all on graded paths (with about a mile of tarmac) and there was nothing really steep or technical anywhere. Obviously, the boundary between trail and fell is blurred - and I'd agree that sections at both Derwentwater and Coniston cross over into fell running country but not at Hawkshead.
In terms of toughness of other trail races, its hard for me to be objective since all the other trail events I have done have been similar. That said, I have seen adverts for other 'trail' races that involve running along canal towpaths, forest roads or through country parks - so I suppose these could be towards the upper end of the difficulty spectrum but that's mostly because they're in the Lake District.