You can do it yourself if you have the time, energy and patience -- according to many answers on the site (do a search for 'Artex' and see what comes up! Alternatively contact local builders -- it's probably worth getting a number of quotes as the work really is tough so it could be pricey.
I used a product called X-Tex. This was very safe as it didnt contain solvents and didnt even effect the plaster board underneath. Left in on overnight and it scraped off the next day with out any effort.