Hmm okay that was weird, closed tekkit down then relaunched it but this time I clicked on the "options" button selected "always use developer build", pressed "okay" to close the settings screen, went back into the settings and changed it back to "always use recommended builds" then pressed the "clear cache" button and when launched Tekkit it downloaded a fresh copy of all of the files and tekkit works fine now, i guess there was a corruption somewhere, case closed.