A short message to the man with long hair and the Guns'n'Roses T-shirt on the 1512 South West Trains service between Waterloo and Basingstoke last Friday:
Yes, it's OK to tie your hair back. In fact, both fashion and work safety demand this to be the case.
However, your sister's hair clips and an Alice band are a no-no and will make you look like a nobber.
Don't be a nobber.