The Rock 'N Tug looks like it's still on the Weymouth Sea Life Centre's website, but since the area seems to be closed for the winter that probably doesn't mean much. I wonder whether they're replacing it with different rides, scaling back on rides or dropping the rides element all together. It doesn't look like they've got many ride to scale back on. It also looks like at some point the Tower has been renamed Jurassic Skyline (wasn't it originally the Weymouth Eye and then something else?). I seem to remember reading that the tower hadn't done that well. I also recall at one time them adding a land train between the Sea Life Centre and the Tower (might be wrong on that one, or it might have been a third party running it?).
There's always a bit of schadenfreude in seeing a Merlin attraction struggling, and I know some people would be pleased if it wasn't just the theme parks taking a hit, but I do have a soft spot for the British seaside and Weymouth. It would be a shame if the Sea Life is being cut back.
Edit: After a quick Google the land train operation was owned by the council, but in 2012 Merlin were given a five year lease on it. The landtrain only runs for the summer but it is mentioned on the website on the 'other tickets' page. The original five year lease may have ended after last summer.