I popped in from third tri to give some advice on the topics stated in the title
This might be more for Canada and USA because I don't think UK has these stores.
For stretch marks I've been using Moringa Nourishing Butter from the Fruits and Passion store. I'm @ 30 weeks and nothing on my tummy (should have used more on my b@@bs at the beginning tho

)
http://www.fruits-passion.com/ But it could be I'm just not prone to stretch marks.
For constipation I've just realized in teh past 2 weeks that Higher-Fibre Low GI White Block Loaf from Cobbs bakery has given me regular "trips" since I've been having a couple of slices a day. The only downer is that their stores are mostly western Canada and Ontario.
http://www.cobsbread.com/ I wish I had found this months ago!
Good luck ladies!!!