mx5cartalk.com

this might help:
viewtopic.php?f=44&t=36608&hilit=radiator+hoses

& don't forget our sponsors: http://www.mx5mania.com.au/product1533.htm

While you can just replace one hose, i.e. the one that is split chances are that the next weakest one will then split as well....

I can only suggest you replace them all. It may cost more in the short term, but it will be much cheaper than a worse case scenario of replacing the head, or engine if a hose completey splits and dumps all of the coolant. Try the forum sponsors or http://www.mx5parts.co.uk

J
ps I have also attached a copy of the NA coolant system, with part numbers.