IMO This series has about the same production values as the early series of the Avengers, i.e. Scenes are shot inside a studio, rather than on location. The action / fight scenes are also on a par with early Avengers, i.e. Reasonably well concieved, but shot in one take with no second chances.
However I disagree with the other reviewer about the quality of the actiing, I don't find it wooden at all, but I do agree that no-one in this show has that X factor of star level charisma, as supplied by Patrick McNee (Stead) or Honor Blackman (Mrs Gale) in the Avengers.
The swinging 60s didn't really kick-off in the mass conciousness until around 1965/66, so it's no surprise not to find much evidence of it here. The Avengers was ahead of the curve in that regard, which is part of the reason why it is considered a classic while this series is almost forgotten.
But if you enjoy Cathy Gale era Avengers you will probably find some entertainment value in this.