I would like to go to one in the Dorset/Hampshire/Wiltshire area, does anyone know where they are being held?

Here's one to get you started:
http://www.britevents.com/whats-on/hampshire/portsmouth/akita-rescue-companion-dog-show/343779/

another:
http://www.southcoastcanineevents.co.uk/pet-dog-show.php

more:
SALISBURY WILTSHIRE SP5 3RT.. on the 6th AUGUST 11-30 JUDGING 12-0clock JUDGE BILLY @ JEANETTE PETRIE ..we have 10.PEDIGREE CLASSES.. @8 NOVELTY CLASSES..FOR BREAK THROUGH CANCER CALL 01722..712373

07 August · 12:00 - 17:00 - Langley Burrell village hall, Chippenham, United Kingdom   SN12 4LL

Dorset:
http://www.buckhamfair.co.uk/schedule.php

Thank you. :)

You're welcome :)
Another good place to look is your local paper, for the "village fete" type ones. I'm trying to work out whether I want to go 10 miles (by bus) on Saturday for a charity show, or a couple of miles (by bus) to a nearby village for their local fete show. As it's forecast to persist with rain all day, I'll get wet whichever I go to! Unless I stay at home of course :)

Just seen that there is one on this Saturday at Ashley Heath Ringwood. Hants.. Sorry dont have any more info as saw it quickly driving into Ringwood for weekly shop.