It feels a bit nuts. But I guess when I did 'Carnage' last year in Font, which is f7b+ (a French grade between V8 and V9 - don't ask...), it took a lot of attempts but at the same time, when it went, it didn't feel like I was at my absolute physical limit, so maybe V11 is possible? It's also about finding the right style of climb at that grade - needs to be crimp-heavy rather than a sloper-fest.
Totally agree on the fear of what you'll hit on the way down. Often more of a problem indoors where someone has thrown a big sticky-outy volume on the next climb over.
Just a form of mantle I think.
Definitely give outdoor bouldering a go. It's much less hassle than setting up a rope. From where you are you could hit up the peak district pretty easily. Burbage South is possibly the best introductory area. Lemme know if/when you do - I'll be much closer to the peaks once I move up north