I am about to buy an annual travelcard, and have noticed that the
offers from various train companies vary quite a bit.

If I buy a Travelcard (three zones) from my local station, I will get
the ticket and a thank you.
But if I buy if from a South West Trains station, I will also, it
appears, receive six free tickets a year to use anywhere on SWtrains.
c2c also offer a weekend ranger ticket at £2.50 per day for Gold Card
holders.

As it is a three zone travelcard, it doesn't really matter what station
is shown on the ticket.
Or, am I missing something major here...?
Billy.