Well the kit came and I installed it this weekend. The Shimano cable sheaths are really good and make it look quite neat.
However, the Merlin kit comes with very long cables (and you cant choose which lengths you receive). The cables are £17 each to buy on their own so I ended up getting the soldering iron out and shortening 3 out of the 4 cables as there was just too much slack to hide anywhere on the frame.
Seems to still work. First ride tonight! :)