If its for studio stuff, may as well get a prime in my view since you don't need the flexibility of a zoom - no point in sacrificing any IQ
Depending on budget of cause, and space you have available, I would recommend:
Sigma 35mm 1.4 - I hear good thing and bad things, worth reading up on - equivalent a 50mm on a FF body, good for a cramped environment.
Canon or Sigma 50mm f/1.4 - Whichever you like the feel/look etc of the best, would make a very nice focal length on a crop body. £230/300
Canon 85mm f/1.8 - Cracking lens, possibly a little long on the focal length with a 1.6 sensor, but great for outdoor portraiture also. £250/300
Tamron 17-50 f/2.8 - also worth a look if you don't like the idea of a prime, I think its a cracking lens on a crop body - IQ is spot on, and its great value for money. £240/300
Unless your seriously thinking of going into portrait/studio/lowlight stuff big time - dont bother looking at the 50mm f/1.2 or 85mm f/1.2, its simply not worth the extra £1000 for the odd picture here and there
My personal recommendation... get a good copy of a Sigma 50mm f/1.4 and you will not regret it.