My pug pup has started swimming with her front paws when in the trot (imagine her if she was stood on 2 paws cleaning windows small circles) What causes this conformationally wise and is there anything i can do to stop it or exercise to build different muscles etc. She hasnt always done it just over the past month or so. I know it greatly puts her down in the ring

From the description it sounds like the movement often termed as 'tied in at the elbow' in horses (where you'll find many explanations and diagrams) and is a conformational fault. Instead of free and forward reach from the shoulder, the leg comes round in an arc with elbows held tightly to the body. An inefficient stride and one which often stems from an incorrectly constructed shoulder/rib  assembly or narrow fore chest.

'tied in at the elbow'

Called the same in dogs and it is for the same reason but difficult to say without seeing best to ask someone with knowledge in the breed. No good asking a vet because unless the dog is lame they do not seem to think there is a problem.

Thanks, off to ask pug people in the know