A month later, I haven't done much else with my solar cells. I took three of the smaller ones and connected them together (correctly this time). I measured a small enough voltage of 0.75V, which is barely enough to overcome the threshold voltages on a transistor or diode. Not a great result, but I'll try more and more.
The main reason I haven't done much is down to the tools and equipment I have. I'm using an ancient old UngarMatic soldering iron. The tips is burnt to a crisp and a single point. Buying new tips is not easy for this model so I decided to bite the bullet and buy a new one.
Now I'm just waiting for my order to come in from Farnell. I bought a Duratool 50W soldering station. It looks fairly good so I'll see how it holds up. I've also bought a number of through hole diodes, resistors, capacitors and a few DIP PIC controllers and ATTINY micro controllers as well. So hopefully I can have a few new things made in the next month or so. Watch this space, more to come soon.