@ecterrab Thank you Edgardo, you have given me a great deal to think about :-)
I completely agree with your comments on Mathematica. The syntax is quite difficult to read, whereas the Maple document looks pretty much the same as a text book or paper.
Thanks to your help, I now have this:
You are quite right about equation lables. It makes it possible to insert and delete and re-execute individual statements. Using %, I often found that it was necessary to re-execute the whole workbook with !!!.
And the intert "%" operator helped with the final substitution in (4.10) :-)
I haven't had time to experiment with pdsolve yet. Presumably it will be necessary to solve for waves propagating allong the x,y and z axies seperately before re-combining?