I might be a bit out of date, but I figured it was better than your post just sitting there, lol.
'What equipment do I need - 6 bottles, brush to clean, steriliser, anything else?'
I can't think of anything else
'Is it true that once babies get used to a certain shape/brand of teat, they refuse other shapes/brands?'
Some do, some don't - it depends on her personality really, lol
'Do teats get worn out with time, and need to be changed?'
yes, how quickly depends on what type you're using
'Rubber or silicone teats?'
www.babydirectory.com/health_clinic/baby/bottle_feeding/171/choosing_the_right_teat_for_your_bottle
though, I think rubber are hard to find?
'I am currently using the slow teats of Medela, suitable for newborn, as I don't want DD to go off the breast completely. How long should I continue using these, and when should I move to medium flow? And why should I move to medium flow teats? DD is sucking very fast and efficient with the slow teats and drinks the bottle in no time...'
if she seems to be getting frustrated while feeding because it's not going fast enough, or starts to get really windy - but that's not as likely to happen with mixed feeding as she'll be used to how it comes out of a breast rather than how it comes out of a bottle
'How does going out with baby in town work - carry a warm prepared bottle in an insulated bag? For how many hours is this milk safe before bacteria starts multiplying?'
this is where I think I might be out of date, lol, I used to make the bottles up, cool them down straight away (in cold running water) and keep them cold, then reheat - warm bottles were a big no no
I genuinely haven't a clue what the current advice is, but you do get little pre-made cartons
'Do babies really stop when they have had enough milk? DD seems to be ready to drink any quantity offered'
That's a problem with mixed feeding, it comes out of a bottle easier and faster, so it is easy to overfeed...stop and wind her every couple of ounces (you might not need to do it as often as that, but that's a good start till you're both used to it), to give her time to register that there's milk in there, lol