That Porsdrill looks the business (although the lassies didn't do the pitch any harm). Thanks so much. My man doesn't have an internet connection, apparently, so I can't give him this link, but I'll print out the thread and pass it on to him. If he can't get it right after all these hints, I'll go over and do it myself.
I don't know what the hole's for but apparently the customer wants to inset something into it and seal the gap with Silicon. The mind boggles. I'll find out and let you know, just out of interest.
Many thanks again.
Al