It depends on what height you are/what height horse your comfortable riding but welsh ponies especially C's can have very animated action and can do well in the dressage sphere.
In fact one of Springfieldpark Unique (by Horeb Euros out of Tinvaal Princess who is by Gwelfro Tywysod) offspring ( Eponas Brenin Mathrafal) is expected to make the Norwegian National Dressage team next year after winning the National Dressage Championships.
Also her first foal Plassens King Daniel by Nebo Daniel is currently competing at Prix. ST George level dressage in Norway.
The Welsh breed is very versitial and strong and if you chose to follow that path I am sure they could carry you to the top of the dressage circuit :)
Good Luck finding your horse :)