Twin Wall flashing for steep pitch...

[Mulberry View]

I'm doing a Chimney stack removal job with my FIL soon. We're going to remove the stack to just over the first floor ceiling, reline the lower part, then covert to Twin Wall.

 

His roof is definitely a little over 45°, but I think it's less than 50°. What's the best type of flashing to use for this?

 

Also, any recommendations on flue suppliers for Twin Wall and Flexible Liner?

[Iceverge]

I used a lead flashing for my parents house when I did this from "Just Lead" in Kent. The flashing was fine but DPD did loose the first one and by the time they returned it to sender it was mangled so I didn't get a refund. 

 

There's a few degrees of play in the lead slate so the 45deg one should be fine. 

 

This is the only pic I could find. We used a 220mm slate tile for a 150mm twinwall flue.