Sounds as though your right caliper simply isn't working properly. I'd say that needed a new rack is complete tosh and anyway the bushes are only £50 on their own. If this came on suddenly, I go for one caliper not applying properly. If the vehicle grabs left, then the left caliper is working and it's the right not pulling its weight. Simple strip, clean and work the pistons in and out to start with. Pretty common. You might need a bigger service, but just check piston movement to start with.