(Yokel,I like your signature,very true)
(This is only my opinion and I know there are PLENTY far more knowing than myself)
I have been told by many Good terriermen,some would call a couple of them,"old timers" I guess,that the Fell Terrier is fully capable of standing on its own,without need of bull blood.In all areas,tenacity,grit,gameness,whatever term you use,desire to stay the course til the job is over.And that there is no benefit whatsoever.
But I think while that may be the case with some,maybe many, I think depending on what you want to accomplish,like a bit bigger,stronge