I had pethedine with birth #1. It wasn't my choice, it was administered without my consent because I was being too loud!
IMO, pehtedine is little more than a chemical restraint. IME It really is a druggy drug, it is a drug! Even down to a nasty come down (it took me a couple of days to start feeling 'with it' again). It led to respiratory issues for my baby as it was administered so close to her birth ~ I was being loud because I was struggling with transition!
If the time came that I struggled with labour to the extent that I truly needed something more than G & A or support, I would opt for epi over pethedine (I was incapable of moving on pethedine anyway!). As it is, I hope this situation wont arise as since birth #1, I have birthed my children at home, using water, homeopathy, great birth partners and active birth principles.
Crowning... breathe, relax, take your time! Go with what you feel, really concentrate on the sensations that occur and shut out external noise to facilitate this if need be. I've used visualisation with all 3 (#4 due any day) and have suceeded in birthing without so much as a scratch. Thus far . It's meant to burn, it will burn! This does not mean you are tearing, don't be afraid just take it easy.