Hello kutarbaby, and thanks for posting your questions here! Let's take a look at them:
1. I''d suggest to start using your Swiss Travel Pass on September 23. That way you'd only need regular tickets for Zurich-Lucerne on September 22, which is quite a short trip. Purchase options are listed at www.myswissalps.com/sw isstravelpass/price. Since you're from the UK, you can best order through www.swisstravelsystem. co.uk.
2. and 5. No, you don't need tickets for the Glacier Express or Golden Pass if you have a Swiss Travel Pass. The Swiss Travel Pass covers both journeys. You'd only need additional seat reservations for the Glacier Express: www.myswissalps.com/gl acierexpress/tickets. Reservations are not obligatory for the Golden Pass, so there's no need to get tickets or book seats for this trip: www.myswissalps.com/go ldenpass/tickets. VIP seats do need reservation.
3. 1st class seats in Golden Pass trains are regular seats in spacious and comfortable carriages with panoramic windows. VIP seats are special seats in the very front of the train, allowing you to enjoy the view from the driver's perspective. Note that not all Golden Pass trains offer VIP seats. Please refer to www.myswissalps.com/go ldenpass for further information.
4. Yes, it will. You'll find a link to timetables at www.myswissalps.com/gl acierexpress/gettingth ere. Glacier Express trains are also included in the general Swiss timetable: www.myswissalps.com/ti metable.
6. Both options are fine in my opinion. It depends on your specific preferences. If you want to make a local scenic trip during your stay in Zermatt (like Gornergrat or Klein Matterhorn) or Interlaken (like Schilthorn or Jungfraujoch), I suggest you review our attraction pages and see what appeals to you. If there's a day trip you're especially interested in, you should spend the extra day in that particular town or area.
7. If want to do part of the Glacier Express, it makes sense to board in Andermatt from Interlaken indeed. It doesn't make sense to do so from Visp, as you'll only enjoy the very last part of the journey to Zermatt in that case. It doesn't really matter which train from Interlaken to Andermatt you take; just pick a connection in the timetable that best fits your scheme. Please note that there's an easier way to travel from Interlaken to Zermatt: first travel to Spiez, then board the local Lötschberg train that runs via Kandersteg and Goppenstein. Once you're in Visp, you can change to a local train towards Zermatt. This isn't the Glacier Express route, but it's still scenic.
8. Yes, just pick any train from the timetable. There are no special scenic trains on this route.