...it would appear that many people are not happy with their services and there are surcharges?
Well, pass can be a good option, but only in very specific set of cases (like really extensive use of trains or not clear itinerary), while in most occasions it's far from being the best option. So let's just take a look at each of your journeys and see what might beat the pass (at least in terms of fare)
London-Paris: surcharge for pass holders here is enormous, so sometimes even ticket bought without pass cost less than surcharge itself. Thus here best option in terms of money is simply to visit
EuroStar website and buy in advance your ticket, discounted offers can be rather low (from 39 GBP), particularly on off-peak departures
Paris-Munich: here your helper is
German Railways website, for the overnight CNL train there is special discounted offer (double cabins start from 99 euro per passenger). Though again, cheap discounted tickets are in limited number, so the earlier you buy the more chances you have to catch cheapest fare.
Munich-Strasbourg: again DB website is the place to start. Three possible options: a) you can purchase in advance discounted international ticket Munich-Strasbourg (from 29 euro per person); b) since Strasbourg is just across the border you can also buy national German ticket from Munich till the last German station (Kehl), in some instances it might be cheaper than option A (Kehl and Strasbourg are connected by public transport); c) if you can't/don't want to purchase discounted tickets in advance, you can simply get daily group pass for all the regional trains in Germany (depending on day of the week either Schones-Wochenende-Ticket or Quer-durchs-Land-Ticket, more on those on our
Germany page), it can be bought even before departure, so allows a lot of flexibility, plus you can make as much stopovers on the way as you like
Strasbourg-Kandersteg: cheapest option here is to get first ticket Strasbourg-Basel (full fare for regional trains is 22,3 euro), while from Basel to Kandersteg you can get discounted Swiss
SuperSaver ticket (from 24,4 CHF), those are the cheapest tickets to travel within Switzerland. Same SuperSaver tickets you can use for your day trips from Kandersteg.
Kandersteg-Venice: since there is anyway no direct connection to Venice, then it makes sense to go with an option of purchasing firsts discounted ticket Spiez-Milan on SBB website (start from 23 CHF), Kandersteg-Spiez is a short and rather cheap ride, so you just will need to be in time in Spiez to board your train to Milan. While from Milan you have two options: a) buy in advance on
TrenItalia website discounted ticket for high-speed train to Venice (from 9 euro, offer called "Super Economy") or, in case you won't be able to do so, just use regional train for only 17,95 euro (that is a full fare, so can be bought even before departure)
Venice-Florence: Again "Super Economy" tickets from TrenItalia website is the cheapest option here (start from 19 euro)
Florence-Orvieto: Full fare for a regional train here is just 15 euro, 20 euro for slightly faster InterCity, while mentioned above Super Economy once again start from only 9 euro. While Orvieto-Rome is just 7,5 euro and connection every hour, so there is nothing to think about here, buy your ticket already at the station and don't worry about any in advance purchase
...the only days it would be nice to have a pass would be when we are in Switzerland and Italy - as there for several days?
There are passes for only a few days, but they are useless in a situation like yours. Mainly because in Switzerland you can use SuperSaver tickets (and even full fare tickets on shorter journeys), while in Italy even full fare tickets (like Orvieto-Rome) is rather cheap, at least much cheaper than daily value of the pass (total price of the pass/#of day it is valid for)
p.s. it is quite a lot of info above, so we suggest you just go over each journey yourself, check websites, offer and fares we mentioned, then compare total to the pass price and at the end you'll see the whole picture regarding pass vs. point-to-point tickets debate.
If something isn't clear or you have further question - we are glad to help