It does depend, but as it happens its generally been pretty good with stuff from Hobbyking, usually about 1-2 weeks.
They've usually got them at the UK Warehouse but out of stock. They have plenty of other servos at the UK Warehouse:
http://www.hobbyking.com/hobbyking/s...tSortOrder=asc
They've got the 1257TG in stock:
http://www.hobbyking.com/hobbyking/s...arehouse_.html it's a little slower but has more torque.