Automated announcements serve a purpose when there are short times between stops, so on services from Wolves/Birmingham to London for example. This gives the TM time to focus on ticket checks.
Stoke/Macc or Crewe/Wilmslow to Manchester going north in the morning, again same principal. If it means catching people who avoid paying whilst others do so, then it has served its purpose.
In regard to long announcements yes a lot of it has to focus on what tickets are and are not valid. If you didn't include it and someone boards with a ticket that isn't allowed then part of their arguement will surely be "I didn't hear that on the announcement". So yes it is covering all bases in that respect. And if it sounds repetitive then remember reasonable warning has to be given to people that if they are on that train and that ticket type isn't allowed then they will be expected to pay upto the correct fare.
Catering announcements... Well it depends on the individual. We are advised to open with a greeting and who you are in order to personalise the service you are offering followed by the fact you are advising people there is a shop service available, key items that you sell and are relevent to the time of day, whereabouts the shop is located, where that shop is (some people still believe it is between standard and first on VWC) and also the payment methods accepted, card types that we take etc.
Then to include some info on promotions such as meal deals or to mention anything we can't offer, say I only have hot water thus can sell instant coffee but not speciality ones.
As for frequency, for me one opening announcement, one maybe after Stoke/Crewe going south and a closing announcement with sufficient warning to make sure everyone gets served. That for me is usually enough and I have to say I have only ever had a handful of complaints over the years about this way of doing it.
