I use a 2x converter and I like it. It brings the subjects so much closer. You do have a small window of focus but it is well worth it.
Thankyou both for your advice.
Andy, I have considered a teleconverter and understand that this increases your focal length but still isn't as useful for macro as extension tubes or dedicated macro lenses. Thanks for the suggestion though.
Maestro, this website looks really good and I will definitely be bookmarking it for future reference. Thanks for the tip.