It may sound drastic but:
1. Take a Stanley knife and cut down along the grain through the middle of the delaminated area.
2. Use a butter knife to get into the cut and prise up one side of the delamiation.
3. Stuff plenty of glue in with a second butter knife.
4. Repeat to the other side.
5. Over the area with some plastic (a shopping bag will do)
6. Place a block of plywood or similar (slightly larger than the delaminates area) on top of the plastic and clamp tightly down. Either with an f or large g clamp. You may need to make a block to fit over the back of the bat so that the jaw of the clamp sits square to the face of the bat.
Leave over night and bobs your uncle.
The plastic prevents the plywood block from sticking to the face of the bat. The plywood spreads the pressure over the delaminated area.
The worse the delamination th easier it is.
For smaller areas I inject glue in using a needle and syringe then clamp in the same way.
This is one I did. Sorry not too good at taking photos during the process.
http://custombats.co.uk/cbforum/index.php?topic=39716.msg629814#msg629814