Purchase advice on 70’s Seiko Grand Quartz Watch

I am in the UK and thinking of buying a 70s Seiko Grand Quartz.
Any advice most welcome ie
1. What models to look out for & avoid.
2.Pros & Cons of various models.
3. How serviceable are these watches.
Can they be repaired?
4. A link to a time line or Brochures & Youtube info.
5. Anyone in the UK selling one? Must be in VGC.
6. Are they over rated when compared with todays Seiko Quartz models?
Thanks in advance