Southern's, Merseyrail's and the former Alphaline's make complaints about SWT's "constant barrage" of announcements seem quite naive...
For those who don't live in SWT-land, almost all of their units use the voice of Celia Drummond, in this pattern on leaving the starting point and principal stations (e.g. Woking):
"Welcome aboard the South West Trains service to Basingstoke, calling at Brookwood, Farnborough, Fleet, Winchfield, Hook and Basingstoke." (gap for the Guard to announce his location)
"Safety information is displayed in all coaches. Do try to keep all personal items with you. If you see anything suspicious, please tell a member of staff."
On the approach to a station, you'll have, for instance,
"The next station is Woking. Change here for Guildford, Aldershot, Farnham, Alton and RailAir coach services to London Heathrow Airport." (If you're approaching a principal station on an intercity route, such as Basingstoke, she'll also remind you to take your personal items with you, and not to leave anything unattended on the station - she also does this when terminating.)
When the doors open, on mainline and intercity services they use, for example,
"This is Brookwood." (pause)
"This train is for Alton. The next station is Ash Vale."
On suburban services worked by 455s, you get, simply,
"This is Hersham. (pause)
This train is for London Waterloo." If it's a major interchange station, she will then go on to announce the calling points (e.g.
"This train is for Shepperton. Calling at Raynes Park, New Malden, Berrylands (etc etc etc)")
The one slightly annoying thing about SWT's default system is the terminating announcement. On approach to the terminus, it lists interchanges and reminds you about belongings - fair enough. However, once the doors are open, it again announces that the train is
"now at its final stop, London Waterloo. On behalf of the on-board staff, thank you for travelling with South West Trains, and we hope you have a pleasant onward journey." It sounds rather long-winded and impersonal, to say the least.
There are also on-demand announcements for smoking, litter, quiet coaches, feet on seats, call NRE about engineering work, etc. I think these are controlled by the Guard.
On the other hand, SWT's class 458 units use the voice of an unidentified male voice actor, "Juniper Man," who is excellent in that he's extremely clear and yet also sounds very excited about everything.

On approach to a station, he will announce, simply,
"we are now approaching--Frimley." No interchange announcements, or anything.
When the doors are unlocked, Juniper Man unleashes his trump card:
"The door buttons are now activated. This is--Aldershot! This train is for--Ascot! The next station is--Ash Vale."
(The only reason I can think of for having "the door buttons are now activated" at the start of these announcements is that the Junipers replaced slamdoor stock, and it announces that so punters don't get confused, or panic that the door's not opening.)
Terminating announcements are far better on the 458s: on the approach, he simply says, for example,
"We are now approaching--Reading--where this train terminates." On arrival, it's something like,
"The door buttons are now activated. This is--London Waterloo--where this train terminates. Thank you for travelling with South West Trains!"
Quick, curt, friendly without sounding saccharine. He's brilliant. Shame he'll be replaced by Celia in all probability when the 458s get refurbished properly.
(Juniper Man also has an announcement for when the train is standing at the terminus prior to departure, listing all the stations - I haven't heard him do this in its entirety, though.)