I needed a new chain for "Malcolm" (the fur covered C5) so went along to Halfords and got two of these ;
..I've used them before on a couple of c5's and they're not too bad. A close fit to the original spec and not too expensive.
The pitch size matches the figures on the tech spec;
http://c5alive.co.uk/forum/index.php?topic=1129.0The chain on the left is the new replacement that I used, the middle chain is the old original Sinclair item and the one on the right is one I tried that is just a bit too small !
You do need a chain breaker to help you remove the excess after joining the two chains , and a set of grips/pliers to push the joining link together - but no other tools are needed.