The 'witches' use masks which resemble goat's heads. However, goats hold absolutely no significance whatsoever to Hecate and her worship. The animal Hecate is most associated with are dogs.
The 'witches' ceremony takes place in the ruins of a church. Hecate being associated with crossroads makes that choice of a location unlikely. Doubly so because Pagans would consider a Christian church a profaned location.
The 'witches' in this show pray to the Goddess Hecate. However, the worship of Hecate is associated with Athens, Thrace and with Greeks from the Anatolian peninsula. So as a Greek Goddess, it's a near impossibility of her being worshiped in Southwestern Britain. The ancestral people of that area are essentially Brythonic and would have worshiped Celtic deities.
On December 21st, Sarah and K-9 need to visit eight local churches before the stroke of midnight. The churches are all within a five mile radius of the house, and K-9 plots the quickest route to visit them all. They set off in broad daylight (the clock on the mantle says it's not even 11:00AM yet, and in England on 21st December, it doesn't get dark until after 4:00PM). By the time Sarah has investigated the sixth church, it is almost midnight. Considering she has a car, and K-9 to assist her in mapping the routes and scanning the area around each church for activity, this is an inordinate amount of time to visit six churches that are all within the local vicinity.