Instead of using a 16MHz crystal, two resistors, a capacitor and a 74LS04 to create my computer's clock, I'm now using an LTC6900 oscillator, which can produce any frequency between 1 kHz and 20 MHz, depending on the value of a resistor. I didn't have any TSOT-23 adaptors, so I made my own using a piece of upside-down stripboard, some super-glue (to hold it in place before it was soldered) and some tiny wires. It works. (As you can probably tell from the neatness (or not) of the soldering, I started on the far side, and finished with the pin in the middle on this side.)

I still have to feed this clock into the CPLD and then take it out to the Z80 (mainly because I like having the option to slow down the clock if I want in the CPLD), but I'm using a 74HCT04 this time, which should be producing the correct voltage for the Z80. Even though it seemed quite happy with the LS version, I thought I'd at least try to be correct.

Oh, and as expected, I had to add a wait state into the ROM access, as going from 8 MHz to 10 MHz has taken it just past the ROM's timing limits.