As stephen said removal is quite easy if you apply heat with a paint stripping heat gun to soften the glue.
To remove the old glue the quickest way for me was as follows,
Mask the area of the new handle to avoid damaging the exposed tubes.
Use an Nylon abrasive wheel connected to a battery drill to remove the old glue (much care is needed as you only want to remove the glue and the finest layer of tube)
Something like this is available from B&Q
Once the glue is off and the area is cleaned with thinners its just a matter of applying the glue and fitting the new handle (you can also use the abrasive wheel on the back of the handle to give a good key for adhesion)
The flap sander also works but I found the abrasive wheel was quicker and more presice