Co-ordination outside the published procedures are subject to traffic levels and controllers workload, Bristol ATC i know had a few aircraft on yesterday avoiding weather so maybe they were busy, they are always helpful.
They were indeed helpful, though they didn't sound very busy (for what RT silence is worth in assessing that) and after a brief time on vectors to the north they pointed me at MALBY with a clearance to join on track MALBY in the climb. So I don't think the actual occupancy of the lower part of L9 was a problem yesterday, though it's helpful to understand the constraints and limitations even so, thank you.
Thanks for all the replies, including by PM. It's all helpful.