Hi philbee and congratulations!
I expressed milk for daily bottles for my older two DC, replacing the expressed feed with formula at around the 6-8 week stage. I have to confess though that with DS3, I haven't expressed at all (don't have time!) and he went straight onto an evening formula feed at about 3 weeks, with all other feeds being breast, and this has worked well.
To be honest, I think providing you wait until breastfeeding is well established before introducing a bottle, and stick to one bottle a day in the early weeks, the nipple confusion thing is a bit of a myth. I can only speak for myself but all three of my babies have had a daily bottle from 2/3 weeks of age and never got nipple confusion at all! But there are a couple of things you'd need to bear in mind in moving straight to formula rather than using expressed milk :
1 - your supply will adjust to take account of that formula feed (as you won't be expressing to give the bottle)
2 - there may be health implications in that the benefits of breastfeeding (protection against allergies etc) might not be quite so effective if formula is introduced.
I decided against giving a bottle late evening because I read that late evening/overnight feeding helps establish milk supply in the early weeks, so we have always offered the bottle in the early evening. DS3 (now 3 months) has a formula feed at about 7pm and this works well for us because he then settles to sleep for a good 4 hour stretch before I bring him into our room for a dreamfeed (breast) at about 11pm. Which means I can then spend a bit of time with my older two at bedtime, reading stories etc without a baby latched to my boob.
However - I did the same thing with DS2 who would take his bottle, sleep 45 minutes and then be awake the rest of the evening! So formula is certainly no guarantee of extended periods of sleep and that is definitely something to be aware of. I have always introduced the bottle to have the flexibility of baby being happy to take either breast or bottle, rather than trying to eke out more sleep, if that makes sense.