Sadly, best thing for crack climbing (at least this is how I got halfway decent at them) is to just climb cracks, and lots of them. I was lucky enough to have a) a 3 month window when I wasn't working and b) the motivation of moving to Yorkshire and as I didn't want to be the stereotypical southerner who can't jam I got stuck in and have to say I found the process painful at times, but hugely rewarding!If you're looking to consolidate at the HVS-ish grade on the odd Peak weekend away I think route choice is going to be paramount - make sure you play to your strengths (there are loads of good non-crack routes at that grade at pretty much every crag), or suck it up and start your crack climbing odyssey ripping yourself apart on Severes!
S: Cuvier Est (Bellvue) - f4, f5, had a million goes on Roxane (6B), guide said not to use the crack, so I tried avoiding it completely, kept falling off after the first move due to no footholds. Looks like the crack is only eliminated for hands, stupid rules!