DRT

Sorry not been back to you lost my broadband connection last week only just got it back. I had a Sample pack of tapes and brochures from Tyvek there was enough of the tape to just seal around the solar HW pipes. I have used a lot of the acrylic tape and double sided tapes from their range and I got them from Huws Gray builders merchants but don't think they have the flexwrap. I found Tyvex to be very helpful with information etc so they could tell you who stocks it.

Have a look at the Tyvek range of tapes. Flexwrap NF may suit you. I used some to seal around the solar thermal pipes coming through the roof. It is pleated so makes it easy to form around odd shapes like pipes ducts etc.