Okay, I finally finished soldering it up. First things first, a few comments on the whole process:
-It was incredibly difficult. I knew it was going to be fiddly, but there was the odd moment when I could have done with an extra pair of hands to hold everything. Even pinning things down with blu-tac wasn't enough when I made a mistake and had to remove a couple of components.
-I've realised that my Antex 21/25W soldering iron is pretty shoddy. The end is too fat and I think there is some sort of residue on the tip so only a small part gets hot enough.
-Stripboard is horrible to work with. The copper strips tend to peel off if a component is soldered then removed. It was also very weak where I had to cut the strips, and frequently started to peel away.
-I tried extremely hard to insulate all bare metal legs/connections, but found that the heatshrink shrank too much axially and ended up leaving the odd part exposed. Even when using insulated wires, the plastic insulation would shrink when the wire was being soldered in.
Despite all the problems I encountered I manage to fit everything in, with only one minor deviation from the hand-drawn plan on the previous page. I was really pleased with this, my hard-work in the planning stage appears to have paid off!
Having soldered it all up I was certain it wouldn't work first time - it was just too much to ask for such a complex circuit on such a small board to work properly first time around. I was right. The LED didn't light up on the first try.
A bit of fiddling with the multimeter showed that there was 9V across the main star ground point and the battery's 9V rail which was obviously not correct - it should have been closer to 4.5V. The LED was not lighting because it was connected over the main ground rail and the 9V rail, thus no voltage across it. A bit of knife action on the back of the board revealed that there was a short from one rail to the other. This was easily cleared.
The LED then lit up, and I was greeted with fully amplified sound!
Sheer delight such as this I had never known before! I was expecting hours of laborious debugging work before it even approached a working state!
Anyway, enough geeky gabbling, here are some more photos to keep you all happy:
Stripboard prepped for soldering. Notice the knife cuts to isolate different parts of the circuit:
The finished circuit! Took me about 3 hours to get to here:
Check out how cramped it is! In particular, note the densely populated top-end, between the 2 coupling capacitors. All the resistors are vertical to save on board real-estate!
The next big challenge is fitting the damn thing into that little aluminium box. I've drawn up some plans for the front panel, and it's very, very tight.
Finally: another warning not to short-circuit 9V batteries. I don't know how this one happened, but it melted through 3 little plastic bags.
I think they're more important than the rail to rail cap. I seem to recall the rail to rail cap is useful in bridged designs.
! Assuming you have a multimeter you should measure only a small voltage loss accross this safety resistor. 
