Andys - males shown natural, females have their manes trimmed, tops of tails shaved and banged - check out http://www.bapshweb.co.uk/ click on events then show turnout, hope that helps.
My TBs were always pulled manes and tails. My arab and natives left natural.
My gypsy cob has a very long mane and tail and I'd would do considerable harm to anyone going near it with a cutting implement after spending so much time caring for it.
I still go next door and pull and plait their horses as I do miss not doing it.
I say it depends on the breed. For example a thoroughbred looks better with a shorter, pulled mane. Cobs look better hogged as it shows off the thickness of their neck. I think you are right about leaving your fresian and your welsh cobs manes long because that suits the breed (I know I just said cobs look better hogged) but welsh cobs are a finer type of cobs so they look better with a mane. x
Depends on breed, horse etc.. I have let by CBXTB horses mane grow as she lives out and I love it. She also used to suffer from keratitis in the bright sunlight but dosn't anymore and i think its because her forelock shields her from the sun. My warmblood has a pulled mane as it it is so thin it would look silly left long