Well, it went OKish:

On the plus side I learned lots from doing this (though no doubt a trivial job to those who have been doing this stuff for ages or are quicker than me), the client's buggy lives on, so I've saved him some money, and Hopper got 15 minutes of fame
.
On the minus side, in retrospect, I could have done it better. Grr! One lives and learns…
Thanks for your help, Robin.