I bought 2 Pro Mini Arduino Compatible boards from eBay (UK) at £2.15 each including shipping.
They are effectively functionally the same as an Arduino Uno but designed to be plugged into a breadboard. It came with male headers for both sides to go under the board to plug into the breadboard and a right angle connection for the serial connection at one end. If you look closely there are 2 pins (holes) at the bottom just above the main row for Analogue 4 & 5. Also, the near end has Analogue 6 and 7 as well as what I think are V++ and GND.
I decided that rather than leaving these pins disconnected would add 3 x 2 pin female headers on the top of the board. So, I bought a bunch of headers from eBay for £1.84. It looks like they have gone up to about £2.64. Still for 10 x 40 male and female headers it’s still cheap.
Add a breadboard and some wires and you have a great prototyping setup.
These are nice little board with some strange design decisions like the 2 x 2 pin headers on the end and the 2 pins for A4 and A5. But by using the female headers it gets around these things. The alternative is to not include A4 and A5 if you don't need all 6 analogue inputs.
Here are some pictures from the build with comments.
|Bits that came in the eBay order|
|Creating 2 pin female headers from 40 pin header|
|Snap off pins. 3rd will fall out. Clean up the edges to fit|
|3 x 2 pin female headers inserted in the top|
|3 x 2 pin headers from the bottom for soldering|
|3 x 2 pin headers soldered up and|
right angle serial header in place for soldering
|All soldered up and ready to be used|
As a side note I also purchased a Leonardo Pro Micro ATmega32U4 Arduino for £3.30