I'm 49 and loved this at the time, as you say, watching it after school on the lead up to Christmas with the great Patrick Troughton as Cole Hawlings.
The series was largely filmed in Shropshire/Worcestershire, just down the road from me using the Severn Valley Railway for the train scenes and local countryside and some wealthy friends of ours lived in the mansion the Harkers lived in, Seakings, it was called Wassell Wood House and we used to go there often including Boxing Day each year. The house was just the same inside only things like TVs and video recorders moved out
Tatchester was actually Tewkesbury
I have it ob DVD by the way. A young Nick Berry was in it too playing Pirate Rat