The clay has 'moist' going on in spades under the brick surface, i'll go arounf the neighbours asking for the contents of their mower hoppers.

Make a friend of a local.tree surgeon and see if you can get a transit load of shredded trees.
If fresh you'll need to compost it yourself, I found 50-50 with fresh lawn mowings.and stirred a little got excellent results, but you mustn't let it dry out & watch out for mould spores when moving it, again water deals with that.
If ready-rotted then dig it in.

Oddly enough i know a tree surgeon, i shall ask him. Is broom ok for normal compost?

Never had any with broom in, but its just a shrub.

Remember, this is a soil structure improver, it will use up some nutrients as it rots away in the soil, so add something slow release with nitrogen to balance it. Makes an excellent weed suppressing mulch and an even better path material.

Manure at 50-50 is a good balancer and some sharp, not builders, sand will further improve structure.