I attended the Cake International show in Birmingham last year and although I was really keen to go to the Cake and Bake show in London, the cost of transport to these shows rapidly eats into my spending budget. But there is another Cake and Bake show in Manchester in 2013 which luckily coincides with my birthday *nudge nudge*
A lot of the shows have the same stalls at each show so I'm not sure of the value to attending EVERY show but they're certainly starting to spread them out throughout the UK which is much better for anyone not based near London. Car sharing is definitely the way forward, I don't think anyone relishes the idea of carrying bags of purchases on trains/buses and the like!
I thought I'd list the shows I know about so far, let me know if you know of anymore: