wxPython Licence vs GPL

[John Perks and Sarah Mount]

we have some Python code we're planning to GPL. However, bits of it were
cut&pasted from some wxPython-licenced code to use as a starting point
for implementation. It is possible that some fragments of this code
remains unchanged at the end.

How should we refer to this in terms of copyright statements and bundled
Licence files? Is there, say, a standard wording to be appended to the
GPL header in each source file? Does the original author need to be
named as one of the copyright holders, or that ours is a derivative work
from his? Which of these would be required under the terms of the
Licence, and which by standard practice / courtesy?

(This assumes the wxPython Licence is compatible with the GPL -- if not,
do we just cosmetically change any remaining lines, so none remain from
the orignal?)

Thanks

John