Stuck Patio Sliding Door
I had a similar problem with an old Wickes Mahogany patio door. Also the cylinder lock had come out as  I fiddled with it. Having read what Jimmy FixIt posted, I:


removed the 2 square, plastic screw covers on the inside handle, 
removed the bolts, 
removed the handle


This revealed at the top a mechanism which I pushed down with a screwdriver.
Taking care not to push the square turning spindle so far in that it falls out the other side of the locked door, put a spanner to the spindle, and, hey presto, it turned. Door unlocked.

Sliding patio doors in a Victorian house on London clay are always going to need adjusting from time to time. I had left it too long and was opening, closing and locking with heft.