Yeah I think it helped that they could recycle the props/costumes from period dramas. Recycling props of course is something that WHO has always done, even in the new series. The classic Dalek props are a good example of this, by the 80s they were still using parts of casing from the 60's-and other props such as the Earthshock human helmets saw a large amount of use as well.
Those helmets were reused in The Mysterious Planet and Delta And Bannermen, but nothing beyond that that I know of.