My answers below in relation to DD:

- how old was baby when you started co-sleeping?
From birth. I put her to bed in her cot and she comes in when she wakes for the first or sometimes second time.

- did your DH/DP sleep in the bed as well, and if not was he okay about being bumped out or did it affect your relationship?
Yes but he starts work very early so is normally up about 2am. Sometimes DS joins us too

- do you sleep on a normal bed or mattress on the floor like the guidelines say?
Normal bed.

- do I really have to sleep with baby on the outside (instead of between DH and I)? I'm scared she'll fall off the bed!
I put her on whichever side she was feeding on. She had her head on my arm so I was always very aware of her.

- what do you have in terms of pillows/sheets/blankets?
I had normal sheets & blankets but not pulled up.

- do I still wrap baby up? And if you monitor room temperature (we have a little gro egg to tell us the temp) what should it be ideally?
No & didn't use.

- how and when did you transition baby back to their own bed?
15mo now & still co-sleeping. She's showing signs of being ready but I couldn't be stuffed re-settling her in her cot lol!

- for daytime sleeps do you put baby in the bed or their own basinette/cot?
In her cot.

I always felt she was safe as I was very aware of where she was, she wasn't a wriggler and I'm a light sleeper. She was also very strong & healthy. It wasn't the most ideal, completely safe environment but I felt the risk was low. What worked for us though, might not work for you. Only you can make that judgement with your baby.