Hi Paula,
Sorry for the delay in coming back to you, I have been advised by our Visa Team that:
We turn around the visa in about 3 weeks. If you send your passport into us as soon as you get your visa pack we can get this processed for you. You will typically receive this 15 weeks before you depart (if you receive your documents by post) or 10 weeks before if you've opted for email documentation.
Kindest regards,
Julia
Edited 28/07/2016 to make sense (sorry to those who read draft 1)