"Now, is this simply a case of getting RST bushes, anti roll bar and adjustable tca's, or will this not fit with the standard 1300 stub axles, and if so, can i fit RST stub axles onto the bottom of my uprated 1300 Bonus dampers "

Hi mate,you can use the bonus hub carrier that you have.Im not sure if youre brackets will be the correct size to hold the thicker RST anti roll bar,but why not get the proper RST brackets when you buy the RST anti roll bar.Should be very easy to get at any RS breaker.
Did the same thing as what youre doing,only i started with a 1400 L shell,so good luck.
Regards Micky