Do you mean Jack Woolgar -Seth Draper, in Present for Sandy?
I can't think who the other one you mean is though
Jack Woolgar had one of those faces that were very familiar, but you could never put a name to it.
I remember he appeared in quite a few different series around that time, usually making one-off appearances.
And someone else who made a lot of guest appearances was William Mervyn, who played the squire.
As far as I know, he only once had a leading role. In the late 60s, he starred in his own series as the detective "Mr Rose".
I remember I was allowed to stay up to watch that every Friday.