Gilly wrote:
If I tackle the job in spring, I can't plant any bulbs this year
(there's no space for them until I dig up and reorganise the
perennials). However, I still have several autumn plants in bloom so
I can't dig up everything right now.


you can't make an omelette without breaking eggs!

Bite the bullet! Dig everything out now. Prepare the ground and replant asap
Things still in growth/flower, heel
in somewhere.

If you compromise the end result will be unsatisfactory

pk